power

Question 1

what is needed for electrical charge to flow through closed circuit

Answer 1

the circuit must induce a potential difference

Question 2

what is electric current

Answer 2

the flow of electrical charge

Question 3

what does current through a component depend on

Answer 3

the resistance and the potential difference across the component. the greater the resistance the smaller the current for a given potential difference.

Question 4

ohmic conductor - resistance, pd and current

Answer 4

current is directly proportional to the pd at a constant temperature. this means resistance remains constant as current changes

Question 5

resistance of filament lamp

Answer 5

it increases as the temperature of the filament increases. graph is an s or f shape

Question 6

diode resistance and current

Answer 6

current in diode flows only one direction because it has a very high resistance in the reverse direction

Question 7

thermistor - resistance and uses

Answer 7

resistance decreases as temperature increases so it is used in fire alarms, ovens, boilers ect. it gets activated once it reaches a certain temperature

Question 8

resistance of LDR and uses

Answer 8

resistance decreases as light intensity increases so used in light sensors or switching on lights automatically - when less light, less resistance so at night it automatically switches on

Question 9

properties of components connected in a series circuit

Answer 9

• current stays the same through each component
• total pd is shared between components
• total resistance of two components is the sum of the resistance of each component

Question 10

properties of components connected in parallel circuit

Answer 10

• pd across each component is the same
• total current through circuit is the sum of currents through separate components
• total resistance of two resistors is less than resistance of smallest individual resistor

Question 11

how adding resistors in each type of circuit effects it

Answer 11

in series circuit it increases total resistance
in parallel circuit it decreases total resistance

Question 12

mains electricity

Answer 12

frequency 50Hz
230 volts
alternating current

Question 13

live wire

Answer 13

brown. carries alternating potential difference from the supply. 230 volts.

Question 14

neutral wire

Answer 14

blue. it completes the circuit. is at or close to 0v

Question 15

earth wire

Answer 15

green and yellow stripes. it’s a safety wire to stop appliance becoming live. at 0 volts unless there is a fault