Physics Experiments PDF

# EXPERIMENT 12 - Finding the refractive index of water using a concave mirror. ## Date: /20 ## Apparatus - Concave mirror of a large focal length - Meter rod - Stand - Knitting Needle - Sharp pointed bright needle - Set square ## Procedure 1. Measure the length of the knitting needle and fin...

# EXPERIMENT 12 - Finding the refractive index of water using a concave mirror. ## Date: /20 ## Apparatus - Concave mirror of a large focal length - Meter rod - Stand - Knitting Needle - Sharp pointed bright needle - Set square ## Procedure 1. Measure the length of the knitting needle and find the index correction between concave mirror and needle. 2. Determine the approximate focal length of the concave mirror. 3. Place the concave mirror on the wooden blocks so that its principal axis is vertical. 4. Clamp the parallax needle horizontally in the stand and place it above the mirror at almost twice the approximate focal length. 5. Remove parallax between the tip of the needle and its image. In this position the needle would be at ‘C’, the center of curvature of the mirror. 6. Hold a meter rod vertically and with a set square note the position of the needle and the pole of the mirror i.c. ОС. 7. Put a few drops of liquid so as to form a small thin layer on the surface of mirror. 8. Again adjust the position of the needle to remove parallax between the tip of the needle and its image at A. 9. Note the position of the needle and applying the index correction between the mirror and the needle i.e. OA. 10. Repeat the experiment twice with concave mirrors of different focal lengths. Finding index of correction in each case. ## Image Description A diagram is drawn showing a stand with a concave mirror on wooden blocks. A needle is clamped horizontally to the stand above the mirror. The needle is labeled 'C' and its reflection is labeled 'A'. The distance between the needle and the mirror is the approximate focal length of the mirror. ## Learn About It - Refractive index of liquid by concave mirror If a small object is placed above a concave mirror containing some liquid in such a way that the image of the object is formed at the same position as the object itself, then the refractive index of the liquid is given by the ratio of the vertical height of its center of curvature to the height of object both measured from the liquid surface. ## Image Description A diagram is drawn of a concave mirror containing a liquid. A small object is placed above the mirror. The image of the object is formed at the same position as the object. The vertical height of the center of curvature of the mirror is labeled 'OC' and the height of the object is labeled 'OA'. ## Precautions 1. Use a concave mirror of a large focal length. 2. Mirror should be horizontal and its principal axis vertical. 3. Distance should be measured very carefully. 4. Parallax needle should be well-illuminated. 5. A small quantity of liquid should be used to get a thin layer on the surface of the mirror. ## Observations & Calculations | No. of. obs. | Position of needle at mirror | Distance | Refractive Index | |---|---|---|---| | | OC (cm) | C (cm) | A (cm) | OC / OA | OA (cm) | n= | | 1 | 0 | 26 | 20 | 26 / 20 | 1.30 | 1.26 | | 2 | 0 | 26 | 19.5 | 25.6 / 19.5 | 1.33 | 1.26 | **Mean refractive index = 1.32** **Result:** The refractive index of water is 1.33, 1.3 # EXPERIMENT 13 - Determining the critical angle of glass using a glass prism ## Date: /20 ## Apparatus - Glass prism or semi-circular slab - Pencil - Protector - Rubber drawing sheet or paper - Common pins - Drawing pins ## Procedure 1. Fix the drawing paper on the drawing board with the help of drawing pins. 2. Place a prism in the center of the paper in such a way that its base is away from you. 3. Mark its boundary ABC with the help of lead pencil. 4. Now remove the prism and fix a pin P on the line AB as shown below. 5. Again place the prism in its previous position. Make sure that the pin P just touches the face AB. 6. Look through the face AC of the prism, you will see the image of pin P. 7. Now move your eyes from C to A slowly, you will find that the image of pin P will become fainter and fainter. A point will reach at which the image seems to disappear. 8. Fix two pins Q and R in such a way that the faintest image of pin P and the pins Q and R become in one line. ## Image Description A diagram is drawn showing a glass prism with its base facing the reader. A straight line AB is drawn through the prism. A pin is placed at point P on the line AB. The pin appears to be at point Q when viewed through the prism. Line QS is drawn from point Q and is extended to point S on the base of the prism. Point D is marked on the surface of the prism. Point M is on line BC. A straight line is drawn from point P to point D and is extended to line BC at point M. Point L is the point where line PD crosses line BC. Line MN is drawn from point M to line BC. 9. Remove the prism and pins. Encircle the pins P, Q, and R. 10. Join Q and R and produce to meet base AC at S. 11. From point P, draw a perpendicular PL on the face BC. Produce PL to D such that PL = LD. 12. Join DS which cuts the line BC at M. 13. At M draw a perpendicular MN on the base BC. 14. Measure the total angle <PMS. 15. Critical Angle i.e c is equal to 1/2 * <PMS = <PMN. 16. Measure the angle PMN which is the critical angle. 17. Repeat this experiment three times and take the mean value of the critical angle c. 18. Calculate the refractive index of the glass from the following relation n = 1 / Sin c ## Image Description A diagram is drawn showing a glass prism with its base facing the reader. A straight line AB is drawn through the prism. A pin is placed at point P on the line AB and appears to be at point Q when viewed through the prism. Line QS is drawn from point Q and is extended to point S on the base of the prism. Point D is marked on the surface of the prism. Point M is on line BC. A straight line is drawn from point P to point D and is extended to line BC at point M. Point L is the point where line PD crosses line BC. Line MN is drawn from point M to line BC. ## Learn About It - Critical Angle When a light ray comes from a denser medium to a rare medium, then it bends away from the normal. So angle of refraction is large as compared with angle of incidence. Also angle of refraction changes with the change of angle of incidence. Finally the angle of incidence for which the angle of refraction becomes 90° is called the critical angle. Critical angle is denoted by c. The relation between the refractive index and critical angle is n = 1 / Sin c where 'n' is the refractive index of glass. ## Observations & Calculations | No. of. obs. | Angle PMS | Critical Angle | |---|---|---| | 1 | 80° | 40° | | 2 | 82° | 41° | | 3 | 79.5 | 39.75 | | | | **Mean critical angle c = 40.2** | | | | **Refractive index n = 1 / Sin c = 1.5** | **Result:** The critical angle of glass is 42° and its refractive index is 1.5. ## Precautions 1. Clean the prism with a cotton cloth.. 2. Mark the boundary of the prism with a sharp pencil. 3. The pins should be vertical. 4. The distance between the pins Q and R should not be less than 5 cm. 5. The pin 'P' should be in the middle of the line AB of the prism. 6. The pin 'P' must touch the surface of the prism. 7. The base of the prism must be away from you. # EXPERIMENT 14 - Tracing the path of a ray of light through a glass prism and measure the angle of deviation ## Date: /20 ## Apparatus - Glass prism - Pencil - Drawing board - Rubber - Common pins - Meter rod - Drawing pins - Protector - White paper ## Procedure 1. Fix a white paper on the drawing board with the help of drawing pins. 2. Place a glass prism in the center of the paper in such a way that its base is towards you. 3. Mark the boundary of the prism ABC. 4. Mark two pins P and Q on the side AB of the prism in such a way that the line PQ must be slanting to it. 5. Observe the image of these two pins P and Q on the other side of the prism (i.e. AC) as shown below. 6. Fix two more pins R and S in such a way that the images of the pins P and Q and these two pins R and S are in a straight line. 7. The distance between pins P and Q, and R and S should not be less than 5 cm. 8. Remove the prism and pins. 9. Encircle the points of pins P, Q, R, and S. 10. Join P and Q, extend PQ which meets the boundary of the prism AB at X. 11. Also join the points S and R and extend SR which meets the boundary of the prism AC at Y. 12. Join X and Y. 13. PQXYRS represents the path of the ray through the prism. ## Image Description A diagram is drawn showing a glass prism with its base facing the reader. A straight line AB is drawn through the prism. A pin is placed at point P on the line AB and appears to be at point Q when viewed through the prism. Line QS is drawn from point Q and is extended to point S on the base of the prism. Point D is marked on the surface of the prism. Point M is on line BC. A straight line called PQ is drawn from point P to point Q. A straight line called RS is drawn from point R to point S. Point X is where line PQ meets line AB. Point Y is where line RS meets line AC. Line XY is drawn. A line labeled 'NL' is drawn perpendicular to line AB from point X. A line labeled 'MN' is drawn perpendicular to line AC from point Y. Point N is the intersection of lines MN and NL. A line labeled 'TOD' is drawn from point T to point O. ## Learn About It - Path of a ray of light through a prism (angle of deviation) ## Angle of Deviation 1. Draw perpendiculars at the point. X and. Y with the help of protector. These perpendiculars are known as normals. and they are denoted by. NL. and. MN. These two normals, meet each other at. N. 2. Measure the angle of incidence i and angle of refraction r. 3. Extend the incident ray PQ forward. and extend. the emergent ray SR backward which meet the incident ray at O. 4. TOS will be the angle of deviation. and is. denoted by D. Measure this angle TOS with the help of protector. Repeat this experiment three times and then take the mean of this. ## Observations & Calculations | No. of. obs. | Angle of incident <i = <PXL | Angle of refraction <r =< NXY | Angle of deviation <TOS = D | |---|---|---|---| | 1 | 53° | 47° | 41° | | 2 | 52° | 36° | 41° | **Mean angle of deviation = 41°** **Result:** The angle between the incidence ray and emergent ray is called angle of deviation. ## Precautions 1. Clean the prism with a cotton cloth. 2. Mark the boundary of the prism with a sharp pencil. 3. The pins should be vertical. 4. The distance between the pins PQ and RS should not be less than 5 cm. 5. The pin 'P' should be in the middle of the line AB of the prism. 6. The pin 'P' must touch the surface of the prism. 7. The base of the prism should be towards you. # EXPERIMENT 15 - Dispersion of light ## Learn About It - Dispersion of light We know that small fragment of colorless glass and precious stones glitter in bright colors when white light is passed through them. This phenomenon was explained by Newton. Newton put a glass in the path of a ray of sunlight. He observed an elongated colored patch of light on the wall. Newton called this a spectrum. This spectrum consists of seven colors. So it means that white light is formed from seven colours. The phenomenon in which white light is decomposed into seven colours is called as dispersion of light. As each colored light has different wavelength that is why it is deviated at different angles. # EXPERIMENT 16 - Verifying Ohm's law (using wire as conductor) ## Date: /20 ## Apparatus - Resistance wire - Rheostat - Key - Voltmeter - Ammeter - Battery - Connecting wires ## Procedure 1. Draw a neat circuit diagram. 2. Make connections according to the circuit diagram. 3. Connect battery, key, rheostat, ammeter and resistance 'R' by means of connecting wires in series. 4. Connect the voltmeter parallel to the resistance 'R'. 5. Before starting the experiment put the plug in the key and adjust the current in the ammeter with rheostat. 6. Note the value of voltage (V).and current (I) from the voltmeter and ammeter respectively. 7. Change the value of voltage by using the rheostat for second and third reading and note the values of voltage and current. ## Image Description A diagram is drawn showing a circuit with a battery, key, rheostat, ammeter, and a resistance. The ammeter is connected in series with the battery, key, rheostat, and resistance. The voltmeter is connected in parallel with the resistance. ## Observations & Calculations | No. of obs | Reading of Voltmeter V (volts) | Reading of Ammeter I (Amp) | R = V / I = constant (ohms) | |---|---|---|---| | 1 | 0.8 | 0.15 | 5.3 | | 2 | 1.0 | 0.19 | 5.2 | | 3 | 1.2 | 0.23 | 5.2 | ## Learn About It * **Resistance:** The ability of a substance to resist the flow of electricity through it is called resistance. It is denoted by a symbol 'Ω'. Its units are Ohm's. * **Rheostat:** Rheostat is a device which is used to control the current in a circuit. It is a variable resistance. * **Voltmeter:** Voltmeter is a device which is used to measure the voltage in a circuit. The unit of a voltage is volt and its symbol is V. * **Ammeter:** Ammeter is a device which is used to measure the current in a circuit. The unit of current is Ampere and it is denoted by 'I'. ### Ohm's Law In 1827 Gorge Simon Ohm a German scientist discovered relationship between the voltage V and current I in a circuit. It states that "The current passing through a wire at constant temperature is directly proportional to the voltage between its ends. **Voltage / Current = constant** or **Voltage / Current = resistance**. So the resistance is a constant quantity and it is the ratio between voltage and current flowing through it. **V/I = R or I = V/R** ## Graph A graph between V and I will give us the relationship between V and I. Take along the x-axis and I on the y-axis. When we join the three points we get a straight line. The straight line means that the voltage V and current I passing through resistance R is directly proportional to the voltage, which is Ohm's Law. **Result:** The current flowing through a conducting wire is directly proportional to the potential difference across each resistor, if temperature remains constant. ## Precautions 1. The ends of wires should be cleaned. 2. Make all the connections tight. 3. Use the key to start and stop the circuit. 4. Pass the current for a short time. 5. Remove the zero error of voltmeter and ammeter. # EXPERIMENT 17 - Studying resistors in series circuit ## Date: /20 ## Apparatus - Two resistance R₁ and R₂ - Voltmeter - Ammeter - Battery - Sand paper - Connecting wires - Key ## Procedure 1. Draw a neat circuit diagram. 2. Make connections according to the circuit shown in the diagram. 3. Take only resistance R, and connect it with key, ammeter and battery in series with the help. of connecting wires. 4. Remember that the. plug of the key should be out while making the connections 5. Insert the plug in the key. the current will start flowing. in the circuit. 6. Note the reading. of voltmeter and ammeter. 7. Determine the value of resistance R₁ by Ohm's law, R₁ = V₁/I₁. 8. Insert the resistance R₂ in place of resistance R₁. 9. Note the readings of voltmeter and ammeter again i.e. V₂ and I₂. 10. Determine the value of R₂ by the formula, R₂ = V₂ / I₂. 11. Connect both the resistance's R₁ and R₂ in series. 12. After inserting. the plug in the key note the readings of voltmeter and ammeter. 13. Calculate the combine resistance of R₁ and R₂ by the following formula. R = V/I where V is the voltage across. R₁ and R₂, and. I is the current flowing. through R₁ and R₂. 14. Note that the resistance R will be equal to the sum of the resistance R₁ and R₂. i.e. R = R₁ + R₂. ## Precautions 1. Clean the ends of the connecting wires with the help. of sand paper. 2. Connections should be tight. 3. Before connecting the circuit remove the plug of key. 4. Always use a voltmeter and ammeter of low range so that deflection may be read clearly. 5. Read the voltmeter and ammeter readings after removing parallex. ## Observations & Calculations Voltage of battery = V = 6 volts | No. of obs. | Current I₁ (A) | Voltage V₁ (V) | Resistance R₁= V₁/I₁ (Ω) | Current I₂ (A) | Voltage V₂ (V) | Resistance R₂=V₂/I₂ (Ω) | Current I (amp) | Voltage V (V) | Net Resistance R=V/I (ohm) |---|---|---|---|---|---|---|---|---|---| | 1 | 0.06 | 6 | 100 | 0.03 | 6 | 200 | 0.02 | 6 | 300 | | 2 | 0.05 | 5 | 100 | 0.02 | 5 | 250 | | | | | 3 | 0.01 | 7 | 100 | 0.05 | 7 | 140 | | | | **Result:** R = R₁ + R₂ = 300 Ω ## Learn About it - Resistors in series In A number of resistors R₁, R₂, R₃ in Ohms are said to be connected in series if they are connected end to end consecutively so that the same current I, in Amperes, flows. through each. If R is the combined resistance and V, in Volts, is the total potential difference across the resistors, then V = IR **But** V = sum of individual pot.diff across R₁, R₂, R₃ V = V₁ + V₂ + V₃ V = IR₁ + IR₂ + IR₃ IR = IR₁ + IR₂ + IR₃ therefore dividing by I, we get R = R₁ + R₂ + R₃ # EXPERIMENT 18 - Studying resistors in parallel circuit ## Date: /20 ## Apparatus - Two standard resistance - Battery - Key - Voltmeter - Ammeter - Connecting wires ## Procedure 1. Draw the circuit. The two resistance R₁ and R₂ are connected in parallel, a voltmeter is also connected in parallel to these resistance. 2. An ammeter, key and battery are connected in series. Ammeters A₁ and A₂ joined in series with resistances R₁ and R₂. 3. Insert the plug of key and note the readings of voltmeter and ammeter. 4. Remember that in parallel combinations of resistance and voltage V remains the same but the current through resistance R₁ will be I₁ and through resistances R₂ will be I₂. 5. The voltage across the net resistances will be V and the total current will be I. i.e. I = I₁ + I₂ 6. The net resistence in parallel can be calculated by using the formula: 1/Req = 1/R₁ + 1/R₂ ## Image Description A diagram is drawn showing a circuit with a battery, key, two resistors, and two ammeters. The two resistors are connected in parallel with each other and with a voltmeter. The battery, key, and two ammeters are connected in series with the resistors. ## Observations & Calculations Voltage of battery = V = 6 volts. | No. of obs. | Voltage V (volts) | Current I₁ (amp) | Current I₂ (amp) | R = V / I (Ω) | R₁ = V / I₁ (Ω) | R₂ = V / I₂ (Ω) | Total resistance 1 / R = (1/R₁ + 1/R₂) (ohms) | |---|---|---|---|---|---|---|---|---| | 1 | 6 | 0.06 | 0.03 | 100 | 200 | 0.015 | | 2 | 4 | 0.04 | 0.01 | 100 | 400 | | | | 3 | 8 | 0.08 | 0.05 | 100 | 160 | | | **Result:** Total resistance = 1/R = reciprocal of ( 1 / 0.015) = 66.7 Ω ## Learn About It - Resistors in Parallel Resistors are said to be in parallel when they are placed side by side and their corresponding ends joined together, as shown in fig. The same potential difference will thus be applied to each, but they will share the main current in the circuit. The main current I divides into I₁, I₂, and I₃, though the resistors R₁, R₂, and R₃ respectively, and that the common potential difference across them is V. If R is the combined resistance, we may write. I = V/R Total current I = I₁ + I₂ + I₃ ... I = V/R₁ + V/R₂ + V/R₃ ... Therefore 1/R= 1/R₁ + 1/R₂ + 1/R₃... Dividing both sides by V, we get 1/R = 1/R₁ + 1/R₂ + 1/R₃... # EXPERIMENT 19 - Verifying the truth table of OR, AND, NOT, NOR, and NAND gates. ## Date: /20 ## Apparatus - D.C power supply (0-6V) - OR gate (7432) - AND gate (7408) - LED indicator module - Two key plugs - Connecting wires ## Learn About It - Logic Gates A circuit that determines whether an input can pass through to the output is called a "logic gate". The three basic types are the AND, OR, and NOT gates. These circuits are the building blocks for other types of logic gates. **The AND gate** AND gate is a logic gate. It works only if both inputs are ON. It will not work if either of the inputs is OFF. The action of AND gate is summarized in the form of truth table. The function of AND gate is explained by a simple circuit. The bulb will be lit only if both switches S₁ and S₂ are closed. **The OR gate** OR gate is also a logic gate. It works if either input is ON or if both are ON, the output is also ON. The action of OR gate is described in detail in the OR truth table. The function of OR gate is explained by the simple circuit, as shown in fig. The bulb will be lit when either or both of the parallel switches are closed. # For AND Gate ## Image Description A diagram is drawn showing an AND gate with two inputs, A and B, and one output Y. Two keys, K₁ and K₂, are connected to the inputs. The output of the AND gate is connected to an LED indicator. Below the diagram is a table showing the truth table for an AND gate. ## Procedure 1. Take an AND gate connect its input terminal A with key K₁ and then with the positive terminal of the power supply. Similarly connect the other input terminal B with key K₂ and then with positive terminal of the power supply. 2. The output terminal of AND gate is connected. with LED indicator and then with negative terminal of the power supply. 3. Keep both key plugs K₁ and K₂ OFF, then there is not any current at inputs A and B, the output LED is also in OFF condition. 4. Put the key plug in K₁ and keeping K₂ OFF then the input terminal A is ON and B is OFF. Then the output terminal 'Y' is also OFF, therefore, LED remains OFF. 5. Put the key plug in K₂ and keeping K₁ OFF then the input terminal A is OFF and B is ON, so output terminal 'Y' is also OFF, therefore, LED remains OFF. 6. Now put the key plugs in both K₁ and K₂, then the both input terminal A and B are ON, at output terminal Y, the LED lighted up which shows that it is ON. **Result:** The output of AND gate is ON if A and B inputs are ON. # For OR Gate ## Image Description A diagram is drawn showing an OR gate with two inputs, A and B, and one output Y. Two keys, K₁ and K₂, are connected to the inputs. The output of the OR gate is connected to an LED indicator. Below the diagram is a table showing the truth table for an OR gate. ## Procedure 1. Take an OR gate, connect its input terminal A with key K₁, and terminal B with key K₂, and then to the positive terminal of power supply. 2. The output terminal of OR gate is connected with LED indicator and then with the negative terminal of the power supply. 3. The working of OR gate is that, if either input is ON or if both are ON, the output is also ON. It can be verified as given. 4. Keeping both key plugs K₁ and K₂ OFF, there is not any current at input terminals A and B. Therefore, the output terminal 'Y' is also OFF, so LED indicator is also OFF. 5. Put the key plug in K₁ and keeping K₂ OFF. The input terminal A is ON and B is OFF. At output terminal Y the LED lighted up which shows it is ON. 6. Put the key plug in K₂ and keeping K₁ OFF, The input terminal A is OFF and B is ON. So at output terminal 'Y'. LED is ON. 7. Now put the key plugs in both K₁ and K₂, then both input terminals A and B are ON. At output terminal. Y, the LED is ON, which verifies the above truth table. **Result:** The output of OR gate is ON if its inputs A or B or both are ON. # For NOT Gate ## Image Description A diagram is drawn showing a NOT gate with one input, A, and one output, B. Key K₁ is connected to input A.. The output of the NOT gate is connected to an LED indicator. Below the diagram is a table showing the truth table for an NOT gate. ## Procedure 1. Take a NOT gate, it has. one input terminal and one output terminal. 2. Connect the input terminal 'A' with the Key K and then to the positive terminal of the 5 volts battery. 3. The output terminal B of the NOT gate is connect with LED indicator and then with negative terminal of the power supply. 4. The working of NOT gate is that if its. input is ON, the output is OFF. If its input is OFF. than output is ON. 5. Keeping the Key plug K OFF the output terminal B is ON, so LED is ON. 6. Put the Key plug in K. The input terminal A is ON. Ai output terminal B, the LED is OFF. **Result:** The output of NOT gate is opposite to its input. # For NOR Gate ## Image Description A diagram is drawn showing a NOR gate with two inputs, A and B, and one output Y. Two keys, K₁ and K₂, are connected to the inputs. The output of the NOR gate is connected to an LED indicator. Below the diagram is a table showing the truth table for a NOR gate. ## Procedure 1. Connect the input terminal A of NOR gate with Key K₁, and terminal B with Key K₂. The both Keys are connected to the positive terminal of the 5 volt power supply. 2. The output terminal NOR gate is connected with LED and also with the negative terminal of 5 volt power supply. 3. The working of NOR gate is that, if either of its inputs is ON or if both are ON, the output will be OFF. This can be verified by truth table as given below. 4. Keeping both Key plugs K₁ and K₂ OFF, there is not any current at input terminals A and B. therefore at the output terminal Y, the LED lighted up, which shows it is ON. 5. Put the Key plug in K₁ and keeping K₂ OFF. The input terminal A is ON and B is OFF. At output terminal Y the LED lights up which shows it is ON. 6. Put the Key plug in K₂ and keeping K₁ OFF. The input A is OFF and B is ON. At output terminal Y the LED lights up which shows it is ON. 7. Now put the key plugs in both keys K₁ and K₂, then both input terminals A and B are ON. At output terminal Y, the LED indicator is OFF which shows it is OFF. **Result:** The output of NOR gate is ON when both of its inputs are OFF. # For NAND Gate ## Image Description A diagram is drawn showing a NAND gate with two inputs, A and B, and one output Y. Two keys, K₁ and K₂, are connected to the inputs. The output of the NAND gate is connected to an LED indicator. Below the diagram is a table showing the truth table for a NAND gate. ## Procedure 1. Take a NAND gate, connect its both input terminals A and B with the key plugs K₁ and K₂ respectively and then to the positive terminal of a 5 volt power. 2. The output terminal of NAND gate is connected with LED indicator and then with the negative terminal of 5 volt power supply. 3. The working of NAND gate is that, both of its input terminals A and B are ON, the output terminal Y is OFF. It can be verified by truth table as given below. 4. Keeping both Key plugs K₁ and K₂ OFF, there is not any current at input terminals A and B therefore, at the output terminal the LED indicator is ON, which shows the output is ON. 5. Put the key plug in K₁ and Keeping K₂ OFF, the input A is ON and B is OFF. At output terminal the LED lights up which shows it is ON. 6. Put the Key plug in K₂ and Keeping K₁ OFF. The input A is OFF and B is ON. At output terminal Y the LED lights up which shows it is ON. 7. Now put the key plugs in both keys K₁ and K₂, then both input terminals A and B are ON. At output terminal, the LED indicator is OFF which shows it is OFF **Result:** The output of NAND gate is OFF when both of its. inputs are ON. ## Precautions 1. For good results use logic bread board. 2. Connection should be tight. 3. Do not use long connecting wires. # EXPERIMENT 20 - Viva Voce Questions for Logic Gates **Q.1. What is AND gate?** **Ans:** AND gate is a logic gate, it works only if both inputs are ON. **Q.2. What is the mathematical notation for AND gate?** **Ans:** The mathematical operation of AND gate is X = A. B Where A and B are input and X is output. **Q.3. If A is ON and B is OFF, what is output of AND gate?** **Ans:** If A is ON and B is OFF, then the output of AND gate i.e. X is OFF **Q.4. What is OR gate?** **Ans:** OR gate is a logic gate. It works if either input is ON or if both are ON. **Q.5. What is the mathematical operation for OR gate?** **Ans:** The mathematical operation for OR gate is X = A + B Where X is output A and B are both inputs. **Q.6. If A = OFF and B = OFF, what is X = ?** **Ans:** For A = OFF, B = OFF, Output X = OFF **Q.7. What are logic gates?** **Ans:** The electronic circuits which convert analogue signals into digital signal are called logic gates. **Q.8. What are characteristics of AND gate?** **Ans:** AND gate gives output only when all the inputs are ON. And gives zero output, when any. one output is zero. **Q.9. What are uses of logic gate?** **Ans:** There is some. logic attached to every operation of logic gate. **Q.10 What do you mean by truth table?** **Ans:** A truth table gives full operation of a logic gate. **Q.11 How many outputs must be provided to AND and OR gate?** **Ans:** There are two or more than two inputs and there is only one output. **Q.12 What is Not gate?** **Ans:** NOT gate is a logic gate. It performs the operation of inversion i.e, it changes a logic level to its opposite level. **Q.13 What is the mathematical operation for NOT gate?** **Ans:** The mathematical operation for NOT gate is X = A Whenever a bar is placed on any variable, it shows that the values of the variable has been inverted. **Q.14 What is. the symbol of NOT gate.** **Ans:** NOT gate is represented by A **Q.15 What is NOR gate?** **Ans:** NOR gate is the combination of OR and NOT. In NOR gate the output of OR gate is inverted. **Q.16 If both the inputs of NOR gate are ON, what is its output?** **Ans:** For NOR, IF A = ON, B = ON then output i.e. x = OFF **Q.17 What is mathematical operation of NAND gate?** **Ans:** The mathematical operation of NAND gate is X = A.B In NAND gate output of an AND gate is inverted **Q.18 What is the symbol of NAND gate?** **Ans:** NAND gate is represented by A _X B