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Current Electricity · Question 106

AIPMT 2001MCQEasy📈 Topic in 38% papers+4−1
1

Copper and silicon are cooled from 300 K to 60 K, the specific resistance

  1. decrease in copper but increase in silicon
  2. increase in copper but decrease in silicon
  3. increase in both
  4. decrease in both

Answer

(1) decrease in copper but increase in silicon

Solution

Copper is a metal: its resistivity decreases as temperature falls (fewer collisions of electrons with lattice ions).

Silicon is a semiconductor: on cooling, the number density of charge carriers falls sharply, so its resistivity increases.

Specific resistance decreases in copper but increases in silicon.

Answer: (1)

AIPMT 2001

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2

The resistance of each arm of the Wheatstone's bridge is 10 ohm. A resistance of 10 ohm is connected in series with a galvanometer then the equivalent resistance across the battery will be

  1. 10 ohm
  2. 15 ohm
  3. 20 ohm
  4. 40 ohm
AIPMT 2001
3

If specific resistance of a potentiometer wire is 10-7 m and current flow through it is 0.1 amp., cross-sectional area of wire is 10-6 m2 then potential gradient will be

  1. 10-2 volt/m
  2. 10-4 volt/m
  3. 10-6 volt/m
  4. 10-8 volt/m
AIPMT 2001
4

The net resistance of the circuit between A and B is [figure]

  1. 83
  2. 143
  3. 163
  4. 223
AIPMT 2000
5

A car battery of emf 12 V and internal resistance 5 10-2 , receives a current of 60 amp, from external source, then terminal potential difference of battery is

  1. 12 V
  2. 9 V
  3. 15 V
  4. 20 V
AIPMT 2000
6

Two bulbs of (40 W, 200 V), and (100 W, 200 V). Then correct relation for their resistances

  1. R40 < R100
  2. R40 > R100
  3. R40 = R100
  4. no relation can be predicted.
AIPMT 2000
7

The potentiometer is best for measuring voltage, as

  1. it has a sensitive galvanometer and gives null deflection
  2. it has wire of high resistance
  3. it measures p.d. in closed circuit
  4. it measures p.d. in open circuit.
AIPMT 2000

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