1. The current through a light bulb connected across the terminals of a 120 V outlet is 0.50 A. At what rate does the bulb convert electric energy to light? 2. A 12.0 V battery causes a current of 2.0 A to flow through a lamp. What is the power used by the lamp? 3. What current flows through a 100. W light bulb connected to a 120. V outlet? 4. The current through a motor is 210 A. If a battery keeps a 12.0 V potential difference across the motor, what electric energy is delivered to the motor in 10.0 s?

1. 60 W

2. 24 W

3. 0.83 A

4. 25200 J

Explanation:

1. What we are simply asked to look for is Electrical Power. It is the rate electrical energy is being transferred.

It is given as:

where I = current and V = voltage.

Therefore, Power is:

P = 0.50 * 120 = 60 W

2. Power, as given in the formula above is:

P = 2.0 * 12

P = 24.0 W

3. According to the formula of Power, current is given as:

=

Power is 100 W and voltage is 120 V, therefore, current is:

4. Recall that power is the time rate of transfer of electrical energy. Mathematically:

where t = time

This means that Electrical energy is:

Recall that Power is:

Therefore, Electrical energy is:

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