Question

1. The rate at which energy is transferred is called _____.

power
resistance
voltage
current

2.The metric unit of electrical power is the _____.
watt
volt
ampere
ohm

3. The power used by an electric tool can be determined by multiplying the _____.
resistance times the current
current times the voltage
resistance times the voltage

4. You are using an electric motor that requires 40 volts to operate. The motor's circuit uses only 5 amps of direct current. How much power is being used?
5 watts
8 watts
40 watts
200 watts

5. What is the advantage of delivering electricity to homes through high voltage lines?

The amount of power available is significantly greater.
The same amount of power is delivered as with moderate voltage without losing energy as heat.
Home appliances are better suited to high voltage.
There is no advantage.

Thank you for your participation!

xoxo
Eli

Answer 1

1. Power.
Power is the rate of energy transfer or the rate at which work is done.

2. watt
Power=energy or work done/time=1 J/1s=1 watt (w)

3. Current times the voltage
E=QV
Q=I times t
E=VIt
p=E/t
p=VIt/t
p=VI

4.200 watts
p=VI=40 x 5=200 W

5. Amount of power available is significantly greater.
p=VI
When V increases, I must go down at the same time so that p doesn’t increase.
Since I is decreased, the power losses due to joule’s heating effect is decreased. The equation representing the energy loss for joule’s heating effect is:
E=I^2Rt
As I is decreased, the energy loss also decreases. Power=energy transferred/time and so as the energy loss due to Joule’s heating effect is decreased, the power loss is also decreased.