1.The potential difference across a length of wire is increased. Which of the fo

Question

1.The potential difference across a length of wire is increased.

Which of the following does not increase as well?

The electric field in the wire.
The power dissipated in the wire.
The resistance of the wire.
The current in the wire.

2

A stereo amplifier creates a 9.0 V potential difference across a speaker.

To double the power output of the speaker, the amplifier's potential difference must be increased to

3. If a 1.8 V battery stores 6.8 kJ of energy (a reasonable value for an inexpensive C cell), for how many minutes could it sustain a current of 1.5 A ?

A stereo amplifier creates a 9.0 V potential difference across a speaker.

To double the power output of the speaker, the amplifier's potential difference must be increased to

25 V 18 V 81 V 13 V

3. If a 1.8 V battery stores 6.8 kJ of energy (a reasonable value for an inexpensive C cell), for how many minutes could it sustain a current of 1.5 A ?

2.1 min 7.0 min 10 min 42 min

Explanation / Answer

1. The resistance of the wire.

2. to double the power V needs to be sqrt(2)V = 1.414xV = 1.414x9 = 13 V

3. Power x time = energy
   V x I x t = Energy

1.8x1.5x t = 6800
   t= 2520 second
   t= 42 minutes

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