energy transfers

Question 1

state 2 equations for the power of the circuit.

Answer 1

P=I V
P=I squared R

power-watts
current- amperes
potential difference= volts
resistance- ohms

Question 2

state an equation linking energy transferred , power and time.

Answer 2

E=p t

energy-joules
power=watts
time=seconds

Question 3

state an equation linking energy transferred , charge flow and potential difference

Answer 3

E= Q V

Energy= joules
charge= coloumbs
potential difference= volts

Question 4

what two main factors does the amount of energy transffered by an appliance depend on

Answer 4

. how long the appliace is being used for

. the power of the appliance

Question 5

describe the energy transfers in a battery powered torch

Answer 5

. battery converts chemical change into electrical change

.bulb converts electrical energy into light as well as waste energy in the form of heating

Question 6

describe the energy transfers in a battery powered motor

Answer 6

.battery converts chemical energy into electrical energy

.motor converts electrical energy into kinetic energy as well as waste energy in the form of heating due to friction

Question 7

what 3 things determine the power of a circuit device

Answer 7

1. the potential difference across the circuit
2. the current through the circuit
3. the amount of energy transferred in a given time

Question 8

what is the purpouse of the national grid

Answer 8

to link power stations to consumers so that they have access to a source of electricity

Question 9

what are the two types of transformers used in the national grid

Answer 9

1. step- up transformers
   2.step-down transformers

Question 10

what are step-up transformers found in the national grid
what do they do

Answer 10

. step- down transformers are used in connecting transmission cables to domestic buildings

.they decrease the potential difference

Question 11

why do transmission lines transfer electricity at high potentials

Answer 11

. at high potentials, results in a lower current

. the lower the current, the less energy that is wasted as heat

. therefore it is more efficient

Question 12

why does the potential need to be decreased between transmission lines and houses

Answer 12

. lower potentials are safer domestic uses and reduces the likelihood of servere electrocution

.appliances are designed for 230V