Power Equations

Question 1

What is the general equation for power?

Answer 1

Power = Energy ÷ time

This equation shows how much energy is transferred per second.

Question 2

What is the equation for energy in terms of power and time?

Answer 2

E = P x t

This equation allows calculation of energy based on power and time.

Question 3

What is the equation for time in terms of energy and power?

Answer 3

t = E ÷ P

This equation allows calculation of time based on energy and power.

Question 4

What units is energy measured in?

Answer 4

Joules (J)

Energy is the capacity to do work and is measured in joules.

Question 5

What units is time measured in?

Answer 5

seconds (s)

Time is the duration of an event and is measured in seconds.

Question 6

What units is power measured in?

Answer 6

Joules per second (J/s) or Watts (W)

Power indicates the rate of energy transfer and is measured in watts.

Question 7

If a kettle has a power of 3000 W and runs for 3 minutes, how much energy does it convert?

Answer 7

540,000 J

Calculation: E = P x t = 3000 x (3 x 60). Time must be converted to seconds.

Question 8

What is the equation for power in electrical circuits?

Answer 8

Power = current x voltage

This equation relates power to current and voltage in electrical systems.

Question 9

What is the equation for current in terms of power and voltage?

Answer 9

I = P ÷ V

This equation allows calculation of current based on power and voltage.

Question 10

What is the equation for voltage in terms of power and current?

Answer 10

V = P ÷ I

This equation allows calculation of voltage based on power and current.

Question 11

What units is current measured in?

Answer 11

Amps (A)

Current is the flow of electric charge and is measured in amperes.

Question 12

What units is voltage measured in?

Answer 12

Volts (V)

Voltage is the electric potential difference and is measured in volts.

Question 13

If a hair dryer has a power of 1.2 kW and operates at 240 V, what is the current flowing?

Answer 13

5 A

Calculation: I = P ÷ V = 1200 ÷ 240.

Question 14

Fill in the blank: Power is measured in _______.

Answer 14

Watts (W)

Watts indicate the rate of energy transfer.

Question 15

Fill in the blank: Energy is measured in _______.

Answer 15

Joules (J)

Joules are a unit of work or energy.

Question 16

True or False: The time in power calculations must always be in minutes.

Answer 16

False

Time must be in seconds for accurate calculations.