Question

The total amount of electrical energy used by a

315-watt television during 30.0 minutes of
operation is
(1) 5.67 × 10^5 J (3) 1.05 × 10^1 J
(2) 9.45 × 10^3 J (4) 1.75 × 10^1 J

Answer 1

`W=Pt`
W - energy, P - power, t - time


`P=315 \ W \\ t= 30 \ min= 30 * 60 \ s = 1800 \ s \\ \\ W=315 * 1800=567000=5.67 * 10^5 \ [J]`

The answer is (1).

Answer 2

The amount of electrical energy used by the television is given by:

`E=Pt`

where P is the power of the device and t is the time.

The power of the television is P=315 W, while the total time is

`t=30.0 min \cdot 60 =1800 s`

If we substitute these numbers into the formula, we find the energy:

`E=Pt=(315 W)(1800 s)=5.67 \cdot 10^5 J`

so, the correct answer is

(1) 5.67 × 10^5 J