Current electricity

The resistivity of a wire depends on:

• 1 Its area
• 2 Its material
• 3 Its current
• 4 Its length

A wire of resistance 4 ohm is stretched to double its length. Its new resistance is:

• 1 2 ohm
• 2 16 ohm
• 3 4 ohm
• 4 8 ohm

Kirchhoff's first law states that at a junction the sum of currents entering equals the sum:

• 1 Of resistances
• 2 Of voltages
• 3 Leaving
• 4 Of charges stored

A cell of emf 6 V and internal resistance 1 ohm drives a current through a 5 ohm resistor. What is the current?

• 1 1.2 A
• 2 6 A
• 3 1 A
• 4 0.5 A

The terminal voltage of a cell is less than its emf because of:

• 1 Temperature only
• 2 Its size
• 3 Internal resistance
• 4 Its colour

In a Wheatstone bridge, the bridge is balanced when the galvanometer shows:

• 1 Zero deflection
• 2 Maximum deflection
• 3 Infinite current
• 4 Negative deflection

The unit of resistivity is the:

• 1 Ohm
• 2 Ohm per metre
• 3 Siemens
• 4 Ohm metre

Internal resistance of a cell makes its terminal voltage ___ the emf when current flows.

• 1 Double
• 2 Greater than
• 3 Less than
• 4 Equal to

Joule's law of heating says that the heat produced is proportional to:

• 1 I R
• 2 R / t
• 3 I² R t
• 4 V / R