Electric Circuits

Question 1

learn the drawings of ciruict symbols

Answer 1

Learn them

Question 2

What is a switch?

Answer 2

Used to turn a circuit on and off

Question 3

What is a lamp?

Answer 3

Electrical current hearts a filament in a bulb that gives out light

Question 4

What is a fixed resistor?

Answer 4

Limits the flow of electrical current
Has a resistance that doesn’t change

Question 5

What is a variable resistor and what is it used in?

Answer 5

Moving slider changes resistance
Used in dimmer switches and volume controls

Question 6

What is a thermistor and what is it used in?

Answer 6

Resistance of thermistor depends on temperature
Used in thermostats or heat activeated fire alarms

Question 7

What is an ldr and what is it used in?

Answer 7

Resistance of ldr depends on light intensity
Used in sensor cameras or automatic light that come on in the dark

Question 8

What is a semiconductor diode

Answer 8

Allows current to flow in one direction
Diodes are used to convert alternating current into a direct current

Question 9

What is an alternating current?

Answer 9

The direction of electron flow continually reverses

Question 10

What is a direct current?

Answer 10

Flow of electrons is consistent around the circuit

Question 11

What are electrons?

Answer 11

Negatively charged particles that transfer energy through wires as electricity

Question 12

What is a charge and what is it measured in?

Answer 12

Property of a body which experiences force in an electric field
Measured in coulombs (C)

Question 13

How do we measure current?

Answer 13

Using an ammeter placed in series with the component

Question 14

How do you measure potential difference in a component?

Answer 14

A voltmeter must be placed parallel with the component

Question 15

What is potential difference measured in

Answer 15

Volts (V)

Question 16

What is the method to investigate how the length of a wire affects its resistance?

Answer 16

1) Connect the parts of the circuit properly
2)Connect crocodile clips to the resistance wire 100 cm apart
3)Record reading on ammeter and voltmeter
4)Move clips closer until 90cm apart
5)Record new readings
6)Repeat steps until the length of wire is minimum 10cm
7)Use R=V/I to calculate resistance

Question 17

What is the method to investigate the relationship between current and potential difference for a resistor, bulb and diode?

Answer 17

1)Connect circuit properly
2)Ensure power supply is zero at start
3)Record readings on voltmeter and ammteer
4)User variable resistor to alter potential difference
5)Record new reading on voltmeter and ammeter
6)Repeat steps 3to four increasing potential difference slightly
7)Reverse the power supply connections and repeat steps 2-6
8)Repeat the experiment but with a bulb

Question 18

What is the relationship between potential difference and current in a fixed resistor?

Answer 18

They are directly proportional
This is called Ohms Law because the resistance of the resistor is fixed and does not change
It is an ohmic conductor

Question 19

What is the relationship between potential difference and current in a lamp

Answer 19

Current does not increase as fast as potential difference
The more energy in the bulb the harder it is for current to flow

Question 20

What happens to current in a series circuit

Answer 20

It’s the same through each component

Question 21

How is resistance shared in parallel curcuits

Answer 21

If resistors are connected in parallel the supply current is divided between them

Question 22

What happens to current in parallel circuits?

Answer 22

Current is split between components on different loops

Question 23

What happens to amount of potential difference in parallel circuits?

Answer 23

It’s the same across each loop

Question 24

What happens to resistance in parallel circuits ?

Answer 24

Reduced as it can follow multiple paths

Question 25

What is the method to investigate resistor networks?

Answer 25

1)Set up the circuit with an ammeter, switch and resistor in a series and then a voltmeter parallel
2)Turn on the power supply and close the switch
3)Record the voltmeter and ammeter readings and calculate resistance with R=V/I
4)Change the resistor and repeat step 2 to find resistance of second resistor
5)Place 2 resistors series to the circuit
6)Record voltmeter and ammeter readings and determine resistance with R=V/I
7)Do it again with resistors in parallel

Question 26

What causes wires in a battery to heat up?

Answer 26

As electrons flow through the wire they collide with the ions in the wire so the ions vibrate more
This increased vibration increases temperature of the wire
Energy has been transferred from the chemical store of the battery to the internal store of the wire