Physics Experiment - Metre Bridge

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Questions and Answers

What is the primary aim of using the half-deflection method in the experiment?

To verify Ohm's law

To measure the voltage across a circuit

To determine the resistance of a galvanometer (correct)

To calculate the total resistance in series circuits

Which formula represents the resistance of the galvanometer in the experiment?

G = R × S

G = R + S

G = R / S

G = R − S (correct)

What precaution should be taken when conducting the resistance measurement experiment?

Connect the plugs loosely in the resistance box

Use wires of varying diameters

Keep the null point within 40 cm to 60 cm (correct)

Ensure the jockey is moved quickly

Which of the following is NOT a source of error in the resistance measurement experiment?

Wires with uniform diameters Signup and view all the answers

When connecting r1 and r2 in series, what should the expected experimental result be?

rs = r1 + r2 Signup and view all the answers

What happens when the jockey in the resistive circuit is rubbed during the experiment?

It can cause erratic readings Signup and view all the answers

What is the figure of merit (k) of the galvanometer represented as?

k = G / S Signup and view all the answers

What should be the expected length measurement for l when obtaining resistance?

Between 40 cm and 60 cm Signup and view all the answers

What is the first step in the procedure for measuring the resistance of the galvanometer?

Insert key K1 and adjust R for maximum deflection. Signup and view all the answers

How is the value of G calculated during the experiment?

By applying the formula $G = R - S$. Signup and view all the answers

What should be done to the key K2 during the experiment?

It should be inserted while keeping R constant. Signup and view all the answers

What is the figure of merit k defined as in the experiment?

Calculated as $k = (R + G) θ$. Signup and view all the answers

Which of the following is NOT a precaution to take during the experiment?

Use a varying e.m.f to observe changes. Signup and view all the answers

What common source of error could affect the measurements taken in this experiment?

Loose screws on the measuring instruments. Signup and view all the answers

When adjusting the value of S, what target deflection value should be achieved?

Exactly half the value of initial deflection θ. Signup and view all the answers

What is the significance of using a high resistance initially in the circuit?

It prevents excessive current from damaging the galvanometer. Signup and view all the answers

What role does the galvanometer play in the metre bridge experiment?

It indicates the null point where there is no deflection. Signup and view all the answers

Which formula represents the relationship between length and resistance in the metre bridge?

$X = \frac{100 - l}{l}$ Signup and view all the answers

What is the main aim of the metre bridge experiment?

To verify the laws of combination of resistances in series. Signup and view all the answers

In the procedure, why is it important to introduce resistance from the resistance box while touching the jockey?

To ensure no deflection in the galvanometer at the null point. Signup and view all the answers

What is a possible source of error when determining resistance using the metre bridge?

Variations in wire thickness along the bridge. Signup and view all the answers

What is the figure of merit in the context of resistance measurement?

The sensitivity of the metre bridge setup. Signup and view all the answers

When the jockey is moved towards the center of the bridge, what should ideally happen to the galvanometer needle's deflection?

It should remain unchanged. Signup and view all the answers

The length marked when there is no deflection in the galvanometer corresponds to which value?

The null point length AD = l cm. Signup and view all the answers

Study Notes

Experiment No. 1 - Metre Bridge - 1

Aim: To determine the resistance of a given wire using the metre bridge.
Materials: Metre bridge, Leclanche cell, galvanometer, resistance box, jockey, one-way key, resistance wire, metre scale, sandpaper, connecting wires.
Theory: The metre bridge, also known as a slide wire bridge, operates based on Wheatstone's bridge principle. A uniform wire is used on a wooden block with two gaps.
Procedure: Arrange the apparatus as shown in the circuit diagram. Connect the unknown resistor in one gap, the resistance box in the other gap, and connect other components as depicted. Adjust the resistance box and use the jockey to find the null point (where the galvanometer shows no deflection). Record the position of the null point and resistance values. Repeat for multiple sets. Calculate the mean value of the unknown resistance.
Precautions: Ensure connections are tight and clean; securely connect plugs in the resistance box; move the jockey gently; keep the null point within the 40-60cm range.
Sources of Error: Loose screws, non-uniform wire diameter, parallax error.
Result: The calculated mean value of the unknown resistance.

Experiment No. 2 - Metre Bridge - 2

Aim: To verify the laws of combination of resistances in series using a metre bridge.
Materials: Metre bridge, Leclanche cell, galvanometer, resistance box, jockey, one-way key, resistance wires, metre scale, sandpaper, connecting wires.
Theory: The metre bridge works on Wheatstone's bridge principle.
Procedure: Similar to Experiment 1, but connect resistors in series in the right gap. Obtain the null point and record the results. Vary the resistance values in the box and repeat.
Precautions: Ensure neat and tight connections, secure plugs, gentle jockey movement, and a null point between 40-60 cm.
Sources of Error: Loose screws, non-uniform wire diameter, parallax error.
Result: Within experimental errors, the combined resistance equals the sum of the individual resistances.

Experiment No. 3 - Half Deflection Method

Aim: To determine the resistance of a galvanometer using the half-deflection method and find its figure of merit.
Apparatus: Weston type galvanometer, battery eliminator, resistance boxes, two one-way keys, rheostat, connecting wires, sandpaper.
Theory: The resistance of the galvanometer (G) is calculated using the formula: RXS / (R+S), where R is the resistance in the box, and S is the shunt resistance needed to reduce the deflection to half). Figure of merit (k) is calculated from the formula: ε / (R+G) * θ
Procedure: Make connections according to circuit diagrams. Calculate the values for R and S that result in a half-deflection using the formula. Repeat the process with different values of R to ensure consistency.
Precautions: All connections must be tight and clean, maintain constant EMF value, use high initial resistance to avoid large current flows.
Sources of Error: Loose screws, inaccurate EMF values, non-uniform size of galvanometer divisions.
Result: Determine the value of galvanometer resistance (G) and calculate its figure of merit (k).

Experiment No. 4 - AC Sonometer

Aim: To determine the frequency of AC mains.
Apparatus: Sonometer, electromagnet, step-down transformer, slotted weights, clamp, stand, paper riders, and connecting wires.
Theory: Alternating current magnetizes an iron core, causing periodic attraction to the sonometer wire, leading to resonance at a specific frequency.
Procedure: Set up the apparatus and determine the resonant length (1) of the wire for a specific load. Measure the length, repeat the experiment with varying loads.
Precautions: Uniform wire, pulley free from friction, stable AC source.
Sources of Error: Non-uniform wire, friction in the pulley, fluctuating frequency of the AC source, incorrect measurements.
Result: Determine the frequency of the AC mains.

Experiment No. 5 - Concave Mirror

Aim: To find the value of 'v' for different values of 'u' in a concave mirror and hence find its focal length.
Apparatus: Concave mirror, mirror holder, illuminated wire gauze, white screen, metre scale.
Theory: The focal length (f) of a concave mirror can be calculated using the formula 1/f = 1/u + 1/v, where u is the object distance and v is the image distance.
Procedure: Place the object at various distances, adjust the screen to obtain a clear image, measure the object distance (u) and the image distance (v), and calculate the focal length using the formula. Repeat for different object distances.
Precautions: Precise measurements, vertical alignment of mirror, object, and screen, no parallax error.
Result: The calculated mean value of the focal length (f) of the concave mirror.

Experiment No. 6 - Convex Mirror

Aim: To determine the focal length of a convex mirror.
Apparatus: Convex mirror, convex lens, illuminated wire gauze, screen, metre scale.
Theory: Convex mirror forms an image of a distant object, and the distance between the mirror and the screen gives the radius of curvature.
Procedure: Use a convex lens to project a clear image of a distant object onto a screen. Introduce the convex mirror between the lens and screen to find the location where the image of the gauze is in alignment with the gauze itself. Measure the distance between the mirror and the screen to get the radius of curvature.
Precautions: Accurate measurements, vertical alignment of mirror, object, and screen, no parallax error.
Result: Calculated mean value of the focal length (f) of the convex mirror.

Experiment No. 7 - Convex Lens

Aim: To determine the focal length of a convex lens by plotting graphs between u and v.
Apparatus: Convex lens, lens holder, illuminated wire gauze, screen, metre scale.
Theory: The focal length (f) of a convex lens can be determined using the formula 1/f = 1/u + 1/v, where u is the object distance and v is the image distance.
Procedure: Place the object at different distances from the lens and obtain a focused image on the screen. Measure the distances u and v and record the data. Plot a graph of 1/u vs 1/v. The slope of this graph gives 1/f and hence f can be obtained.
Precautions: Precise measurements, correct vertical alignment of the lens, object, and screen, no parallax error.
Result: The determined focal length (f) of the convex lens from the graph.

Experiment No. 8 - Concave Lens

Aim: To determine the focal length of a concave lens using a convex lens in contact.
Apparatus: Convex lens, concave lens, illuminated wire gauze, screen, lens holders, scale.
Theory: The focal length of the combined lens system (F) can be determined using the formula 1/F = 1/f1 + 1/f2. where f1 is the focal length of the convex lens and f2 is the focal length of the concave lens.
Procedure: Determine the focal length (f1) of the convex lens as per the given procedure (similar to convex lens experiment). Then combine the convex lens and concave lens. Measure the focal length of the combined lens system (F). Find the focal length (f2) for the concave lens using the formula. Repeat experiments for multiple combinations and then average results.
Precautions: Accurate measurements, vertical alignment of the lenses, object, and screen, no parallax error. Correct selection of convex lens.
Result: The calculated mean value of the focal length (f2) of the concave lens.

Activity A1 - Ohm's Law Circuit

Aim: To assemble an electrical circuit with the appropriate components and measure the current and voltage values.
Apparatus: Unknown resistor, battery, voltmeter, ammeter, rheostat, key, connecting wires.
Theory: Ohm's Law (V = IR) states that the current flowing through a conductor is directly proportional to the voltage applied across it.
Procedure: Connect components according to circuit diagram, adjust the rheostat value to vary current, and measure voltmeter and ammeter values.
Precautions: Correct connections, constant voltage/current (using rheostat), good quality components.
Result: Obtain the calculated resistance value.

Activity A2 - Circuit Correction

Aim: Correct a given circuit diagram to include all necessary components connected in proper order.
Apparatus: Battery, resistor, voltmeter, ammeter, rheostat, key, connecting wires.
Theory: Voltmeters are connected in parallel; ammeters are connected in series. Rheostats control current.
Procedure: Identify components connected incorrectly in the diagram. Draw and connect the corrected circuitry. Test and measure readings using the corrected circuit.
Precautions: Verify correct connections, use appropriate ranges for instruments.
Result: Correct circuit diagram.

Activity A3 - Potential Gradient

Aim: To study the relationship between potential drop and wire length for a constant current.
Apparatus: Uniform wire, voltmeter, battery, rheostat, key, jockey, connecting wires.
Theory: Potential gradient is constant for a uniform wire carrying a constant current.
Procedure: Connect components as shown in the diagram. Vary the wire length and measure the corresponding voltage drops. Calculate the potential gradient for each set of readings.
Precautions: Use a uniform wire, consistent current, and accurate measurements
Result: Calculate potential gradient values.

Activity B1 - Light-Dependent Resistor (LDR)

Aim: To test the impact of changing light intensity on an LDR.
Apparatus: LDR, light source, multimeter.
Theory: LDR resistance decreases with increasing illumination.
Procedure: Measure the resistance of the LDR at different distances from the light source.
Precautions: Maintain a constant light source intensity at each measurement point.
Result: The resistance of the LDR decreases as the distance from the light source decreases.

Activity B2 - Identifying Components

Aim: To identify diodes, LEDs, resistors, and capacitors in a mixed collection.
Apparatus: Diodes, LEDs, resistors, capacitors, multimeter.
Theory: Different components have unique electrical characteristics, which can be identified using a multimeter.
Procedure: Use a multimeter in different modes to identify components based on their characteristic behavior.
Precautions: Ensure proper use of the multimeter setting to avoid damage to the components, and be cautious not to short-circuit the components.
Result: Identify the components.

Activity B3 - Convex Lens Image Formation

Aim: To analyze the nature, size, and position of images formed by a convex lens for different object positions.
Apparatus: Convex lens, screen, candle, matchbox, scale.
Theory: Image formation depends on the object's position relative to the lens focal length.
Procedure: Position the object at different locations relative to the lens (infinty, beyond 2f, at 2f, between f and 2f, at f, and within f) and obtain focused images on the screen. Observe and record the nature (real/virtual, inverted/erect), size, and position of the image for each location. Draw the ray diagrams for each position.
Precautions: Use a consistent light source to ensure the object is visible.
Result: Describe the nature, size, and position of the image for various object positions. Draw ray diagrams to illustrate each case.

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Description

This quiz focuses on Experiment No. 1 involving the metre bridge to determine the resistance of a wire. Students will learn about the setup, theory, and procedure for conducting the experiment. Key concepts include the operation of the metre bridge and the application of Wheatstone's bridge principle.