current electricity - Test 01

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In the given network each resistance is 2 ohm . The resistance between A and B is

• 1 ohm
• 2 ohm
• 3 ohm
• 4 ohm

Which of the following characteristics of electrons determines the current in a conductor?

• Drift velocity alone.
• Thermal velocity alone.
• Both drift velocity and thermal velocity.
• Neither drift nor thermal velocity.

A copper wire of length 1 metre and radius 1 mm is joined in series with an iron wire of length 2 metre and radius 3 mm and a current is passed through the wire. The ratio of current density in the copper and iron wire is

• 18:1
• 9:1
• 6:1
• 2:3

In a wire of circular cross section with radius r free electron travel with drift velocity v when a current i flows through the wire what is the current in another wire of half the radius and same material when the drift velocity is 2v

• 2 i
• i
• i/2
• i/4

The potential difference of V is applied at the ends of copper wire of length l and diameter d on doubling only diameter drift velocity

• becomes two times
• becomes half
• does not change
• becomes one fourth

For a cell of terminal potential difference in open circuit 2.2 V, reduces to 1.8 V when cell is connected across a resistance of 5 ohm. The internal resistance of the cell is

• 10/9 ohm
• 9/10 ohm
• 11/9 ohm
• 5/9 ohm

• a
• b
• c
• d

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

• 16:1
• 1:16
• 1:4
• 4:1