JEE Physics Current Electricity MCQs Set A

Question: Electric current has both magnitude and direction. It is a

• a) Scalar quantity
• b) Tensor quantity
• c) None of these
• d) Vector quantity

Answer: Scalar quantity

Question: Identical piece of Ge and Cu are taken and cooled, then

• a) Resistivity of Cu decreases and Ge increases
• b) Resistivity of both decreases
• c) Resistivity of both increases
• d) Resistivity of Cu increases and Ge decreases

Answer: Resistivity of Cu decreases and Ge increases

Question: A current of 10 A is maintained in a conductor of cross-section 1 cm². If the number density of free electrons be 9 × 10²⁸ m^–3, the drift velocity of free electrons is

• a) 6.94 × 10^–6 m/s
• b) 5.94 × 10^–2 m/s
• c) 1.94 × 10^–3 m/s
• d) 2.94 × 10^–4 m/s

Answer: 6.94 × 10^–6 m/s

Question: A potential difference of 5 V is applied across a conductor of length 10 cm. If drift velocity of electrons is 2.5 × 10^–4 m/s, then electron mobility will be

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question:

• a) 1.875 × 10¹⁹
• b) 1.875 × 10¹⁸
• c) 1.875 × 10¹⁷
• d) 1.875 × 10¹⁶

Answer: 1.875 × 10¹⁹

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Ohm's law fails in

• a) All of these
• b) PN junction system
• c) Thyristor
• d) Diode

Answer: All of these

Question:

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question: f a copper wire is stretched to make its radius decrease by 0.1%, then the percentage increase in resistance is nearly

• a) 0.4%
• b) 0.2%
• c) 0.8%
• d) 0.1%

Answer: 0.4%

Question: A certain piece of copper is to be shaped into a conductor of minimum resistance. Its length and diameter should respectively be

• a)

  

• b)

  

• c)

  

• d) L, D

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A piece of wire is cut into four equal parts and the pieces are bundled together side by side to form a thicker wire. Compared with that of the original wire, the resistance of the bundle is

• a)

  

• b)

  

• c)

  

• d) The same

Answer:

Question: Two wires A and B of the same material, having radii in the ratio 1 : 2 carry currents in the ratio 4 : 1. The ratio of drift speed of electrons in A and B is

• a) 16 : 1
• b) 1 : 16
• c) 1 : 4
• d) 4 : 1

Answer: 16 : 1

Question: The temperature co-efficient of resistance of a wire at 0°C is 0.00125 °C^–1. At 25°C its resistance is one ohm. The resistance of the wire will be 1.2 ohm at

• a) 190°C
• b) 225 K
• c) 260°C
• d) 185 K

Answer: 190°C

Question: A conductor behaves as a superconductor

• a) At critical temperature
• b) At boiling point of that metal
• c) Above critical temperature
• d) At 100°C

Answer: At critical temperature

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 3
• b) 2
• c)

  

• d)

  

Answer: 3

Question: A wire has resistance 12 ohm. It is bent in the form of a circle. The effective resistance between the two points on any diameter of the circle is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A technician has only two resistance coils. By using them singly, in series or in parallel, he is able to obtain the resistance 3, 4, 12 and 16 ohms. The resistance of the two coils are

• a) 4 and 12 ohms
• b) 7 and 9 ohms
• c) 4 and 16 ohms
• d) 6 and 10 ohms

Answer: 4 and 12 ohms

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

More Questions..............................

Question: The resultant resistance value of n resistances each of r ohms and connected in series is x. When those n resistances are connected in parallel, the resultant value is

• a)

  

• b)

  

• c)

  

• d) nx

Answer:

Question:

• a)

  

• b)

  

• c) 12 R
• d) 3 R

Answer:

Question:

• a) V = E + i r
• b) V = E – i r
• c) V = E
• d) Zero

Answer: V = E + i r

Question:

• a) +1 volt
• b) –2 volt
• c) –1 volt
• d) +2 volt

Answer: +1 volt

Question:

• a) 10 V
• b) 8 V
• c) 6 V
• d) Zero

Answer: 10 V

Question:

• a) 7 V
• b) 8 V
• c) 6 V
• d) 5 V

Answer: 7 V

Question:

• a) 3 A
• b) 4 A
• c) 12 A
• d) 16 A

Answer: 3 A

Question:

• a) 6 A
• b) 5 A
• c) 4 A
• d) 1 A

Answer: 6 A

Question: Thousand cells of same emf E and same internal resistance r are connected in series in same order without an external resistance. The potential drop across 399 cells is found to be

• a) Zero
• b) 399 E
• c) 601 E
• d) 1000 E

Answer: Zero

Question: Five cells each of e.m.f. E and internal resistance r are connected in series. If due to over sight, one cell is connected wrongly, then the equivalent e.m.f. of the combination is

• a) 3 E
• b) 4 E
• c) 2 E
• d) 5 E

Answer: 3 E

Question: Two batteries of different e.m.f.'s and internal resistance connected in series with each other and with an external load resistor. The current is 3.0 A. When the polarity of one battery is reversed, the current becomes 1.0 A. The ratio of the e.m.f.'s of the two batteries is

• a) 2
• b) 2.5
• c) 1.5
• d) 1

Answer: 2

Question:

• a) 1.33 volt
• b) 2 volt
• c) 1.60 volt
• d) 0.80 volt

Answer: 1.33 volt

Question:

• a) 0.2 A
• b) 0.3 A
• c) 0.4 A
• d) 0.1 A

Answer: 0.2 A

Question:

• a)  R = 6 ohms
• b)Potential difference between A and B is 2 V
• c) R = 8 ohms
• d) R = 10 ohms

Answer: R = 6 ohms

Question:

• a)

  

• b)

  

• c)

  

• d) 1 A

Answer:

Question:

• a) Does not change
• b) Decreases
• c) Increases
• d) First increases then decreases

Answer: Does not change

Question:

• a) B
• b) A
• c) First A then B
• d) It will remain at C

Answer: B

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 2 : 3
• b) 5 : 1
• c) 3 : 2
• d) 1 : 5

Answer: 2 : 3