JEE Mains Current Electricity Past Paper PDF

Subject: Physics\ Topic: Current Electricity\ Total Questions: 35 (15 Integer type, 20 MCQs) Integer-Type Questions ====================== 1\. A wire of resistance 20 Ω is bent to form a square. Find the equivalent resistance between two opposite corners of the square. 2\. In a circuit, two resis...

Subject: Physics\ Topic: Current Electricity\ Total Questions: 35 (15 Integer type, 20 MCQs) Integer-Type Questions ====================== 1\. A wire of resistance 20 Ω is bent to form a square. Find the equivalent resistance between two opposite corners of the square. 2\. In a circuit, two resistors of 10 Ω and 20 Ω are connected in parallel and then in series with a 5 Ω resistor. Calculate the total resistance. 3\. A 10 V battery is connected across a 5 Ω resistor. What is the current flowing through the resistor? 4\. A potentiometer wire has a length of 1 m and a resistance of 4 Ω. Find the potential gradient if a 2 V cell is connected across the potentiometer. 5\. A wire has a resistance of 9 Ω. It is stretched to double its length. What will be the new resistance? 6\. Calculate the current passing through a 2 Ω resistor if a potential difference of 12 V is applied. 7\. Find the power dissipated in a 4 Ω resistor when a current of 3 A flows through it. 8\. A cell of EMF 5 V and internal resistance 0.5 Ω is connected to an external resistance of 9.5 Ω. What is the current in the circuit? 9\. In a Wheatstone bridge, if the resistances in the ratio arms are 3 Ω and 5 Ω, what should be the resistance of the unknown resistor if the bridge is balanced and the fourth resistor is 10 Ω? 10\. Two resistors of resistance 2 Ω and 3 Ω are connected in series. Find the current if a 10 V battery is connected across the combination. 11\. In a galvanometer, the current required for full-scale deflection is 2 mA. If the galvanometer has a resistance of 50 Ω, find the shunt resistance required to convert it into an ammeter of range 1 A. 12\. A heater coil has a resistance of 30 Ω and is connected to a 120 V power supply. Calculate the heat produced in 10 seconds. 13\. Calculate the drift velocity of electrons in a copper wire of cross-sectional area 10\^-6 m\^2 when a current of 5 A flows through it. The number density of electrons is 8.5 x 10\^28 m\^-3. 14\. A capacitor of 5 µF is charged by a 12 V battery and then connected to a resistor of 2 MΩ. Find the time constant of the circuit. 15\. The resistance of a conductor increases by 20% when its temperature is raised from 27°C to 127°C. Calculate the temperature coefficient of resistance of the material. Multiple Choice Questions (MCQs) ================================ 16\. A current of 2 A flows through a conductor when a potential difference of 6 V is applied. What is the resistance of the conductor?\ A) 2 Ω\ B) 3 Ω\ C) 4 Ω\ D) 1 Ω 17\. If the current through a conductor doubles, how does the power dissipated in the conductor change?\ A) Doubles\ B) Halves\ C) Quadruples\ D) No change 18\. Two resistors, 4 Ω and 6 Ω, are connected in series and a voltage of 20 V is applied. What is the power dissipated in the 6 Ω resistor?\ A) 8 W\ B) 12 W\ C) 10 W\ D) 4 W 19\. A 60 W bulb is connected to a 120 V supply. What is the resistance of the bulb?\ A) 240 Ω\ B) 480 Ω\ C) 2 Ω\ D) 120 Ω 20\. Which of the following is true for a parallel circuit?\ A) The total resistance is greater than any of the individual resistances\ B) The voltage is the same across all resistors\ C) The total resistance is equal to the sum of individual resistances\ D) The current is the same through all resistors 21\. A wire has a resistance of 8 Ω. If its length is doubled, what will be its new resistance?\ A) 4 Ω\ B) 16 Ω\ C) 32 Ω\ D) 2 Ω 22\. The internal resistance of a cell decreases with\ A) Increase in current\ B) Increase in temperature\ C) Decrease in temperature\ D) Increase in EMF 23\. A copper wire of length 2 m and cross-sectional area 1 mm² has a resistance of 0.34 Ω. What will be the resistance of a wire of the same material with length 4 m and cross-sectional area 2 mm²?\ A) 0.68 Ω\ B) 0.17 Ω\ C) 1.36 Ω\ D) 0.34 Ω 24\. In a series circuit, which of the following remains constant across all components?\ A) Voltage\ B) Current\ C) Power\ D) Resistance 25\. The resistivity of a material depends on\ A) Length\ B) Cross-sectional area\ C) Material\ D) Temperature and material 26\. In an electric circuit, the potential difference across the ends of a resistor is 10 V and the current passing through it is 5 A. What is the resistance?\ A) 0.5 Ω\ B) 50 Ω\ C) 2 Ω\ D) 5 Ω 27\. The power dissipated in a resistor of resistance 10 Ω when a current of 3 A flows through it is:\ A) 30 W\ B) 90 W\ C) 9 W\ D) 10 W 28\. Which law states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant?\ A) Ohm\'s Law\ B) Kirchhoff\'s Voltage Law\ C) Kirchhoff\'s Current Law\ D) Joule\'s Law 29\. The SI unit of electric resistivity is:\ A) Ohm\ B) Ohm-meter\ C) Coulomb\ D) Ampere 30\. The energy dissipated in the form of heat in a resistor when a current \'I\' flows through it for a time \'t\' is given by:\ A) P = IV\ B) H = I²Rt\ C) P = I²R\ D) H = V²/R 31\. The total current supplied by the battery in a parallel combination of resistors is equal to:\ A) The current through the smallest resistor\ B) The current through the largest resistor\ C) The sum of the currents through each resistor\ D) None of the above 32\. The electric power consumed in a circuit is given by:\ A) V²/R\ B) IR\ C) V/I\ D) I²V 33\. A wire of resistance R is stretched to double its length. What will be the new resistance?\ A) R/2\ B) 2R\ C) 4R\ D) R/4 34\. A resistor of 8 Ω is connected in parallel with a 4 Ω resistor. The equivalent resistance is:\ A) 12 Ω\ B) 8 Ω\ C) 2.67 Ω\ D) 6 Ω 35\. Which instrument is used to measure current in a circuit?\ A) Voltmeter\ B) Ammeter\ C) Galvanometer\ D) Ohmmeter 36\. Consider a current carrying wire (current I ) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is \(a) source of emf. \(b) electric field produced by charges accumulated on the surface of wire. \(c) the charges just behind a given segment of wire which push them just the right way by repulsion. \(d) the charges ahead. 37\. A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100Ω. He finds the null point at l 1 = 2.9 cm. He is told to attempt to improve the accuracy. Which of the following is a useful way? \(a) He should measure l 1 more accurately. \(b) He should change S to 1000Ω and repeat the experiment. \(c) He should change S to 3Ω and repeat the experiment. \(d) He should give up hope of a more accurate measurement with a meter bridge. 38\. Two cells of emf's approximately 5V and 10V are to be accurately compared using a potentiometer of length 400cm. \(a) The battery that runs the potentiometer should have voltage of 8V. \(b) The battery of potentiometer can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10V. \(c) The first portion of 50 cm of wire itself should have a potential drop of 10V. \(d) Potentiometer is usually used for comparing resistances and not voltages. 39\. Which of the following characteristics of electrons determines the current in a conductor? \(a) Drift velocity alone. \(b) Thermal velocity alone. \(c) Both drift velocity and thermal velocity. \(d) Neither drift nor thermal velocity. 40\. Kirchhoff 's junction rule is a reflection of \(a) conservation of current density vector. \(b) conservation of charge. \(c) the fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction. \(d) the fact that there is no accumulation of charges at a junction. 41\. Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors: \(a) number of charge carriers can change with temperature T. \(b) time interval between two successive collisions can depend on T. \(c) length of material can be a function of T. \(d) mass of carriers is a function of T. 42\. The drift velocity of electrons in a conducting wire is of the order of 1mm/s, yet the bulb glows very quickly after the switch is put on because \(A) The random speed of electrons is very high, of the order of 106 m/s \(B) The electrons transfer their energy very quickly through collisions \(C) Electric field is set up in the wire very quickly, producing a current through each cross section, almost instantaneously \(D) All of above 43\. A current passes through a wire of non-uniform cross-section. Which of the following quantities are indepen- dent of the cross-section? \(A) the charge crossing in a given time interval (B) drift speed \(C) current density (D) free-electron density. 44\. When no current is passed through a conductor \[Shifted SSI Sir 2012-13\] \(A) the free electrons do not move \(B) the average speed of a free electron over a large period of time is zero \(C) the average velocity of a free electron over a large period of time is zero \(D) the average of the velocities of all the free electrons at an instant is zero 45\. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of : \(A) each of the them increases (B) each of them decreases \(C) copper increases and germanium decreases (D) copper decreases and germanium increases 46\. In an electric circuit containing battery, the positive charge inside the battery \(A) always goes from the positive terminal to the negative terminal \(B) may go from the positive terminal to the negative terminal \(C) always goes from the negative terminal to the positive terminal \(D) does not move. 47\. The efficiency of a cell when connected to a resistance R is 60%. What will be its efficiency if the external resistance is increased to six times. A. 80 % (B) 90% (C) 55% (D) 95% 48\. If 2 bulbs rated 2.5 W -- 110 V and 100 W -- 110 V are connected in series to a 220 V supply then \(A) 2.5 W bulb will fuse (B) 100 W bulb will fuse \(C) both will fuse (D) both will not fuse 49\. Three equal resistors connected in series across a source of emf together dissipate 10 watts of power. What would be the power dissipated if the same resistors are connected in parallel across the same source of emf ? \[JEE - 1972\] A. 60 watt (B) 90 watt (C) 100 watt (D) 30 watt 50\. A 50 W bulb is in series with a room heater and the combination is connected across the mains. To get max. heater output, the 50 W bulb should be replaced by : \(A) 25 W (B) 10 W (C) 100 W (D) 200 W