BITSAT Physics Current Electricity MCQs

Question: A wire is connected to a battery between the point M and N as shown in the figure (1). The same wire is bent in the form of a square and then connected to the battery between the points M and N as shown in the figure (2). Which of the following quantities increases?

• a) Heat produced in the wire and resistance offered by the wire
• b) Resistance offered by the wire and current through the wire
• c) Heat produced in the wire, resistance offered by the wire and current through the wire.
• d) Heat produced in the wire and current through the wire

Answer: Heat produced in the wire and current through the wire

Question: In the circuit shown in figure the current through

• a) The 3 Ω resistor is 0.50 A
• b) The 3 Ω resistor is 0.25 A
• c) The 4 Ω resistor is 0.50 A
• d) The 4 Ω resistor is 0.25 A

Answer: The 4 Ω resistor is 0.25 A

Question: A meter bridge is set up as shown, to determine an unknown resistance ‘X’ using a standard 10 ohm resistor. The galvanometer shows null point when tapping-key is at 52 cm mark. The endcorrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of ‘X’ is

• a) 10.2 Ω
• b) 10.6 Ω
• c) 10.8 Ω
• d) 11.1 Ω

Answer: 10.6 Ω

Question:  Two resistances at 0° C with temperature coefficient of resistance α1 and α2 joined in series act as a single resistance in a circuit. The temperature coefficient of their single resistance will be

• a) α1 + α2
• b)

  

• c)

  

• d)

  

Answer:

Question: The drift velocity of electrons in silver wire with cross-sectional area 3.14 × 10–6 m2 carrying a current of 20 A is. Given atomic weight of Ag = 108, density of silver = 10.5 × 103 kg/m3.

• a) 2.798 × 10^–4 m/sec.
• b) 67.98 × 10^–4 m/sec.
• c) 0.67 × 10^–4 m/sec.
• d) 6.798 × 10^–4 m/sec

Answer: 6.798 × 10^–4 m/sec

Question: In the circuit shown in the figure, find the current in 45 Ω

• a) 4 A
• b) 2.5A
• c) 2 A
• d) 3.5 A

Answer: 2 A

Question: A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if

• a) Both the length and the radius of the wire are halved.
• b) Both the length and the radius of the wire are doubled.
• c) The radius of the wire is doubled
• d) The length of the wire is doubled.

Answer: Both the length and the radius of the wire are doubled.

Question: The resistance of a wire is R. It is bent at the middle by 180° and both the ends are twisted together to make a shorter wire. The resistance of the new wire is

• a) 2 R
• b) R/2
• c) R/4
• d) R/8

Answer: R/4

Question: Two long coaxial and conducting cylinders of radius a and b are separated by a material of conductivity σ and a constant potential difference V is maintained between them, by a battery. Then the current, per unit length of the cylinder flowing from one cylinder to the other is –

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A wire X is half the diameter and half the length of a wire Y of similar material. The ratio of resistance of X to that of Y is

• a) 8 : 1
• b) 4 : 1
• c) 2 : 1
• d) 1 : 1

Answer: 2 : 1

Question: What should be the characteristic of fuse wire?

• a) High melting point, high specific resistance
• b) Low melting point, low specific resistance
• c) High melting point, low specific resistance
• d) Low melting point, high specific resistance

Answer: Low melting point, high specific resistance

Question: In the circuit shown in figure potential difference between points A and B is 16 V. the current passing through 2Ω resistance will be

• a) 2.5 A
• b) 3.5 A
• c) 4.0 A
• d) zero

Answer: 3.5 A

Question:  Three voltmeters A, B and C having resistances R, 1.5 R and 3R, respectively, are connected as shown. When some potential difference is applied between X and Y, the voltmeter readings are V_A, V_B and V_C respectively. Then –

• a) VA ≠ VB = VC
• b) VA = VB ≠ VC
• c) VA ≠ VB ≠ VC
• d) VA = VB = VC

Answer: VA = VB = VC

Question: Calculate the effective resistance between A and B in following network.

• a) 5 Ω
• b) 10 Ω
• c) 20 Ω
• d) 30Ω

Answer: 20 Ω

Question: The power dissipated in the circuit shown in the figure is 30 Watts. The value of R is

• a) 20 Ω
• b) 15 Ω
• c) 10 Ω
• d) 30 Ω

Answer: 10 Ω

Question: Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?

• a) Drift speed
• b) Resistivity
• c) Resistance
• d) Number of free electrons

Answer: Number of free electrons

Question: The length of a potentiometer wire is l. A cell of emf E is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will be the same cell give a balance point.

• a) 2l/3
• b) l/2
• c) l/6
• d) 4l/3

Answer: l/2

Question: In a Wheatstone bridge all the four arms have equal resistance R. If the resistance of galvanometer arm is also R, the equivalent resistance of combination is

• a) 2R
• b) R/4
• c) R/2
• d) R

Answer: R

Question: Potentiometer measures potential more accurately because

• a) It measures potential in open circuit
• b) It uses sensitive galvanometer for null deflection
• c) It uses high resistance potentiometer wire
• d) It measures potential in closed circuit

Answer: It measures potential in open circuit

Question: A cell of internal resistance r is connected across an external resistance nr. Then the ratio of the terminal voltage to the emf of the cell is

• a)  

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In the circuit shown, when the switch is closed, the capacitor charges with a time constant

• a) RC
• b) 2RC
• c) (1/2) RC
• d) RC ln 2

Answer: RC

Question: In the electric network shown, when no current flows through the 4W resistor in the arm EB, the potential difference between the points A and D will be :

• a) 6 V
• b) 3 V
• c) 5 V
• d) 4 V

Answer: 5 V

Question: When a current I is set up in a wire of radius r, the drift velocity is v_d. If the same current is set up through a wire of radius 2 r, the drift velocity will be

• a) 4 v_d
• b) 2 v_d
• c) v_d / 2
• d) v_d/4

Answer: v_d/4

Question: The effective resistance between points P and Q of the electrical circuit shown in the figure is –

• a)

  

• b)

  

• c) 2r + 4R
• d)

  

Answer:

Question: What should be the characteristic of fuse wire?

• a) High melting point, high specific resistance
• b) Low melting point, low specific resistance
• c) High melting point, low specific resistance
• d) Low melting point, high specific resistance

Answer: Low melting point, high specific resistance