TOPIC 2//Circuits/I-V/Parallel and Series circuit/Current/Resistance

Question 1

Define current

Answer 1

Flow of electric charge around a closed circuit if there is a potential difference

Question 2

Define Potential difference

Answer 2

the driving force that pushes the charge round

Question 3

Define resistance

Answer 3

anything in the circuit which slows the flow of charge down

Question 4

How can you relate current with resistance

Answer 4

the Greater the resistence, the smaller the current that flows through

Question 5

How does Charge, time and current relate

Answer 5

Q-IT

Question 6

What is charge measured in

Answer 6

Coulumbs

Question 7

How does resistance, current and pd relate

Answer 7

V=IR

Question 8

Describe the IV characteristics of an ohmic conductor

Answer 8

at a constant temperature, the current flowing through ohmic conductor is directly proportional to PD across it so resistance doesnt change with current

Question 9

Describe IV characteristics of Filament lamp

Answer 9

when electrical charge flows through a filament lamp, it transfers some energy to thermal energy store of filament which is designed to heat up so resistance will increase

Question 10

Describe IV characteristic of a diode

Answer 10

The resistance depends on the direction of the current through a diode which only flows in one direction

Question 11

Describe the method of investigating resistance

Answer 11

1. Attach 1st crocodile clip to the wire at 0cm
2. attach 2nd clip at 10cm
3. write down the length of the wire you are testing
4. close the switch and record current through wire and PD across it
5. open switch then move 2nd clip another 10cm along wire
6. close switch and record new length, current and PD
7. Repeat this a few times
8. use measurement of current and pd to calculate resistance. R=V/I

Question 12

Describe Ohmic conductors

Answer 12

Current through an ohmic conductor at a constant temp is directly proportional to Potential difference so you get a straight line

Question 13

Describe Filament lamp

Answer 13

as the current increases, the temperature of filament lamp increases, so resistance increases. This means less current can flow per unit pd so graph is a curve

Question 14

Describe a Diode

Answer 14

Current will only flow through a diode in one direction.The diode has very high resistance in reverse direction

Question 15

What is an LDR

Answer 15

a resistor that is dependant on intensity of light
in bright light, resistant falls
in darkness, resistance is highest

Question 16

What is a Thermistor

Answer 16

Temperature dependant resistor
in hot conditions, resistance drops
in cool conditions, resistance goes up

Question 17

what are 4 things about series circuits

Answer 17

1. if you remove or disconnect one component, the circuit is broken and they all stop
2. potential difference adds up
3. Current is the same everywhere
4. Resistance adds up

Question 18

What are the 4 things about parallel circuits

Answer 18

1. if you remove or disconect components, it will hardly affect circuit
2. potential difference is the same everywhere
3. Current is shared
4. Adding a resistor in parallel reduces total resistance