Dynamic Electricity: Electrical Power & Energy

Question 1

Describe electrical power.

Answer 1

The amount of work the device can perform

Determined by how much energy (Joules) a device consumes in a given unit of time (seconds)

Question 2

The more powerful the device….

Answer 2

• The quicker it works

- The more work it does in a given time

Question 3

How is electrical power determined?

Answer 3

Pe= E/t

Pe: electrical power (Watts)
E: energy (Joules)
t: time interval (Seconds)

Pe=VI

Question 4

If a motor A consumes 2x as much energy in 3hrs as motor B. Which is more powerful?

Which does more work?

Answer 4

A is more powerful.

A does more work.

Question 5

How is electrical energy determined?

Answer 5

E=(Pe)(t)

E: Energy (J)
Pe: Power (W)
t: time (Secs)

OR (kw x h)=(kw)(h)
(w x h)=(w)(h)

Energy is calculated by multiplying electrical power by the time

Question 6

What are the formulas?

Answer 6

V=IR
P=VI
E=Pt
P=E/t
kwh= (kw)(h)

Question 7

A toaster uses 10A of current on a 120V line.

1. What is the power?
2. How much energy does the toaster use if it takes three minutes to make toast?
3. How many kwh?

Answer 7

1. 1200W
2. 216000j
3. 0.06kwh

Question 8

The resistance of a heating element on your stove top is 10ohms and the potential difference across its terminals is 240V. It is used for 3h. How much electrical energy was used during this period?

Answer 8

E=17.28kwh

Question 9

What is the symbol for energy? What is it measured in?

Answer 9

Symbol: E

Measure in Joules (j) or kilowatt hours (kWh)

Question 10

A TV is used for an average of 6h a day and draws 160A of current from a 110V outlet. If power is $0.086kWh how much will it cost per day?

Answer 10

$9.08

Question 11

PRACTICE PROBLEMS AT BACK OF PACKAGE AND WORKSHEET

Answer 11

do them.