Energy And Power

Question 1

Give the definition of power.

Answer 1

Power is the rate at which work is done.

Question 2

How can the work done in a resistor be investigated?

Answer 2

Using a CALORIMETER.

Question 3

The work done is equivalent to [what]?

Answer 3

The energy transferred.

Question 4

What is the equation to finding work done?

Answer 4

W = i^2RT

[I squared x resistance x time]

Question 5

Give the names and units of the following symbols;
1] w [unit?]
2] I
3] R
4] t

Answer 5

1] work done [joules - J]
2] current [amperes - A]
3] resistance [ohms - **]
4] time [seconds - t]

Question 6

What is work done also known as?

Answer 6

Energy

Question 7

Give the equation to finding power: [there are actually 3 ** asking teacher]

Answer 7

P = W/t

Question 8

Give the names and units of the following symbols;
1] P
2]W
3]t

Answer 8

1] power - watts
2] work done - joules
3] time - seconds

Question 9

If energy is measure in joules, and power is measure in joules per second… what is one watt equal to?

Answer 9

One joule per second

Question 10

If energy is measure in joules, and power is measure in joules per second… what is one watt equal to?

Answer 10

One joule per second

Question 11

The term ‘watt’ is the unit for power and describes?

Answer 11

The rate at which energy is used by an electrical device.

Question 12

When paying for the electricity in our homes, the cost is not expressed in joules OR seconds. What units of measurement are used?

Answer 12

• express the power in kilowatts
• express the time in hours

Therefore, the cost is not expressed in joules, rather kWh killowatts per hour

Question 13

To how many watts is one kilowatt [kwh] equal to?

Answer 13

1,000 watts / 1,000 joules of energy per seconds.

Question 14

What does a ‘kilowatt-hour’ mean?

Answer 14

It means that one kilowatt of power has been used for one hour.

Question 15

How do you determine the killowatt-hours of electricity used?

Answer 15

Kilowatt-hours = kilowatts x hours

Question 16

Kilowatt-hours = kilowatts x hours

Generally you will have to fine the kilowatts first before finding the kilowatt-hours. How would you go about this?

Answer 16

1] #watts x 1kilowatt/1000 watts = kilowatts
2] kilowatts x hrs = kilowatt-hours

Eg. You use a 1500 watt hair heater for 3 hrs. How many kilowat-hours of electricity do you use?

1] 1500 watts x 1 kilowatt/1000 watts = 1,5 kilowatts
2] 1.5 kilowatts x 3 hrs = 4.5 kilowatt-hours of electricity was used.