P2- Current Electricity

Question 1

Opposites..

Answer 1

Attract.

Question 2

Objects with the same electric charge..

Answer 2

Repel each other.

Question 3

How can we calculate current?

Answer 3

I= Q/t

I= current in amperes (A).

Q= charge in coulombs (C).

t= time in seconds (s).

Question 4

How does an insulator become negatively charged?

Answer 4

It gains electrons.

Question 5

What circuit symbol is this?

Answer 5

Switch (open)

The switch enables the current to be switched on or off.

Question 6

What circuit symbol is this?

Answer 6

Switch (closed)

The switch enables the current to be switched on or off.

Question 7

What circuit symbol is this?

Answer 7

Cell

A cell is needed to push electrons around a complete circuit.

Question 8

What circuit symbol is this?

Answer 8

Battery

A battery consists of two or more cells.

Question 9

What circuit symbol is this?

Answer 9

Ammeter

An ammeter measures electric current.

Question 10

What circuit symbol is this?

Answer 10

Voltmeter

A voltmeter measures potential difference (voltage).

Question 11

What circuit symbol is this?

Answer 11

Motor

Question 12

What circuit symbol is this?

Answer 12

Lamp

Emits light when a current passes through it.

Question 13

What circuit symbol is this?

Answer 13

Fuse

Designed to melt if current going through it is greater than a certain amount➡️Breaks circuit

Question 14

What circuit symbol is this?

Answer 14

Fixed resistor

Limits the current in a circuit.

Question 15

What circuit symbol is this?

Answer 15

Variable resistor

Allows current to be varied.

Question 16

What circuit symbol is this?

Answer 16

Light dependent resistor

Question 17

What circuit symbol is this?

Answer 17

Diode

Allows current through in one direction only.

Question 18

What circuit symbol is this?

Answer 18

Light-emitting diode

Emits light when a current passes through it.

Question 19

What circuit symbol is this?

Answer 19

Heater

Transfers electrical energy to heat the surroundings.

Question 20

How can we calculate potential difference (voltage)?

Answer 20

V=W/Q

V= Potential difference in volts (V).

W= work done in joules (J).

Q= charge in coulombs (C).

Question 21

How can resistance be calculated?

Answer 21

R=V/I

R= resistance in ohms (Ω).

V= potential difference in volts (V).

I= current in amps (A).

Question 22

Where should voltmeters always be placed in relation with the measured component?

Answer 22

In parallel.

Question 23

What is resistance?

Answer 23

Resistance is the opposition to current flow.

Question 24

What is the unit of resistance?

Answer 24

Ohms.

Question 25

Where should ammeters be placed in relation to the measured component?

Answer 25

In series.

Question 26

What is Ohm's law?

Answer 26

Ohm's law states that the current through a resistor at constant temperature is **directly proportional** to the potential difference across the resistor.

Question 27

What does this graph show and why?

Answer 27

A current-potential difference graph for a filament light bulb. The line is a curve because the wire gets hotter for larger currents.

Question 28

What does this graph show and why?

Answer 28

A current-potential difference graph for a diode. The current only flows in one direction so in reverse direction the diode has very high resistance so the current is zero.

Question 29

What does this graph show?

Answer 29

A resistance-temperature graph for a thermistor. As the temperature increases, the resistance decreases.

Question 30

What does this graph show?

Answer 30

A resistance-light intensity graph for a light-dependent resistor. As light intensity increases, resistance decreases.

Question 31

What happens in a series circuit if one component stops working?

Answer 31

No current flows. This is because in a series circuit, they are all connected one after the other and there is only one route for the charge to flow.

Question 32

How could you find the total potential difference in a series circuit?

Answer 32

Add all the individual potential differences.

Question 33

How could you find the total resistance in a series circuit?

Answer 33

Add all the individual resistances.

Question 34

What happens in a parallel circuit if one component stops working?

Answer 34

Current can't flow to that one component, but can flow to all the other components. This is because each component is connected across the supply.

Question 35

How could you find the total current in a parallel circuit?

Answer 35

Add the individual currents.

Question 36

How could you find the total voltage in a parallel circuit?

Answer 36

In a parallel circuit the potential difference is the same across each component.

Question 37

How does current depend on resistance in a parallel circuit?

Answer 37

The bigger the resistance of a component, the smaller the current is.

Question 38

What circle symbol is this?

Answer 38

Thermistor.

Question 39

Why is it important that ammeters have very low resistance?

Answer 39

So the ammeter reduces the current as little as possible.

Question 40

The resistance of the bulb increases as the potential difference across the bulb increases. Why?

Answer 40

Temperature of bulb increases.