Power Of Electrical Appliances

Question 1

what are electrical appliances designed to do

Answer 1

transfer energy to components in the circuit wen a current flows

Question 2

explain how kettles work

Answer 2

they transfer energy electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle

Question 3

explain how a handheld fan works

Answer 3

energy is transferred electrically from the battery of the fan to the kinetic energy store of the fans motor

Question 4

what does a higher current result in

Answer 4

the more energy transferred to the thermal energy stores of the components, and then the surroundings

Question 5

what does energy being radiated to the surroundings suggest about the efficiency of the appliances

Answer 5

all of the energy transferred isnt useful energy

Question 6

how do you calculate the efficiency of the an electrical appliance

Answer 6

(useful output energy transfer / total input energy transferred) x 100

Question 7

if you only know the power input and output, how do you calculate the efficiency of an electrical appliance

Answer 7

useful energy output / total power input

Question 8

what does the total energy transferred by an appliance depend on

Answer 8

how long the appliance is on for and its power

Question 9

what is the power of an appliance

Answer 9

the energy that it transfers per second, so the more energy it transfers in a given time, the higher its power

Question 10

what is the formula for working out the energy transferred

Answer 10

energy = power x time (J = W x s) or E = Pt

Question 11

what do appliances given a power rating labelled with

Answer 11

the maximum safe power that they can operate at

Question 12

what is the second thing power ratings on an appliance are labelled with

Answer 12

the maximum amount of energy transferred between stores per second when the appliance is in use

Question 13

how do power ratings help customers

Answer 13

they can choose between models, the lower the rating, the less electricity the appliance uses in a given time so the cheaper it is to run

Question 14

what happens when en electrical charge goes through a change in potential difference

Answer 14

the energy is transferred

Question 15

what is the formula for calculating energy transferred in a circuit

Answer 15

energy transferred = charge flow x potential difference (E = QV)

Question 16

if the formula for energy transfer is correct, what does it mean for a battery with a bigger potential difference

Answer 16

it will supply more energy to the circuit for every coulomb of charge which flows around it, as the charge is raised up higher at the start

Question 17

after the energy is transferred from the change in pd, what happens

Answer 17

energy is supplied to the charge at the power source to raise it through a potential

Question 18

what is the formula for calculating the power of an appliance

Answer 18

power = potential difference x current (P =VI) or W =VA

Question 19

how can you find out the power of an appliance if you dont know the potential difference

Answer 19

adding V = IR into P = VI to get P = I^2R