Electricity

Question 1

What is a switch?

Answer 1

used to turn a circuit on and off

Question 2

What is a resistor

Answer 2

reduces the flow of a current

Question 3

What is a fixed resistor?

Answer 3

a fixed resistor has a resistance that doesn’t change

Question 4

What is a variable resistor?

Answer 4

adjusting this resistor changes its resistance

a variable resistor is used in some dimmer switches and volume controls

Question 5

What is a thermistor?

Answer 5

the resistance of a thermistor depends on its temperature
at low temperatures the thermistor has a high resistance
as the temperature increases, the resistance increase
can be used in thermostats or heat activated fire alarms

Question 6

What is an LDR? (Light Dependant Resistor)

Answer 6

the resistance of an LDR depends on light intensity
at low light levels the LDR has a high resistance
as the light intensity increases, the resistance decreases
can be used as a sensor in cameras or automatic lights

Question 7

What is a diode?

Answer 7

allows a current to flow in one direction but not in the other

Question 8

What is an ammeter?

Answer 8

measures the current (rate of flow of charge)

Question 9

What is a voltmeter?

Answer 9

measures the potential difference (energy transferred per unit charge)

Question 10

What is a current and what is it measured in?

Answer 10

the rate of flow of charge

Amps

Question 11

What is the potential difference/voltage and what is it measured in?

Answer 11

the energy transferred per unit charge

volts

Question 12

What is the rule for current in a series circuit?

Answer 12

the current stays the same everywhere in the circuit

Question 13

What is the rule for current in a parallel circuit?

Answer 13

the current flows around the circuit from the power supply, then splits when it reaches a junction and rejoins at the second junction

Question 14

What is the rule for potential difference in a series circuit?

What is the equation

Answer 14

The voltage of the power supply is split between the bulbs in the circuit
v1 = v2 + v3

Question 15

What is the rule for potential difference in a parallel circuit?

Answer 15

the voltage of each bulb is the same as the power supply

v1 = v2 = v3

Question 16

What is the rule for resistance in a series circuit?

Answer 16

the more resistors in the circuit, the higher the resistance

Question 17

What is the rule for resistance in a parallel circuit?

Answer 17

the more resistors, the lower the resistance

Question 18

Fill the gaps :

____ resistance will reduce the flow of current

___ resistance will allow a high current to flow

Answer 18

high resistance will reduce the flow of current

low resistance will allow a high current to flow

Question 19

How is resistance caused? (three points)

Answer 19

• an electric current flows when electrons move through the conductor, such as a metal wire
• the moving electrons can collide with the ions in the metal
• this makes it more difficult for the current to flow, and causes resistance

Question 20

What is resistance?

Answer 20

a measure of how much the electrical current is reduced by a component

Question 21

What is resistance measures in?

Answer 21

Ohms (Ω)

Question 22

How do you calculate the current?

What are the measurements used?

Answer 22

current = charge / time

Amps) (coulombs) (seconds

Question 23

How do you calculate potential difference? (2 different calculations)

What are the measurements?

Answer 23

potential difference = energy / charge
(volts) (joules) (coulombs)

potential difference = current x resistance
(volts) (amps) (ohms)

Question 24

What is charge measured in?

Answer 24

coulombs (C)

Question 25

How do you calculate the resistance?

What are the measurements?

Answer 25

resistance = potential difference / current

(ohms) (volts) (amps)

Question 26

Fill the gaps :

As the ______ of a wire increases, the resistance ________

As the __________ increases, the resistance ________

Answer 26

as the length of a wire increases, the resistance increases

as the temperature increases, the resistance increases

Question 27

Why does the resistance increase if the temperature increases?

Answer 27

as the wire gets hotter, the particles gain more kinetic energy and vibrate more
this makes it harder for a current to flow through the wire, so the resistance will increase

Question 28

What is ohms law?

for a conductor, . . .

Answer 28

for a conductor, the potential difference of the component will be directly proportional to the current flowing through it provided the temperature remains constant