Electricity and circuits T5

Question 1

What is current?

Answer 1

The flow of electric charge around a circuit. Unit : ampere

Question 2

What is the potential difference?

Answer 2

The potential difference (or voltage) is the driving force that pushes the charge around. Unit : volt. The potential difference is the energy transferred per coulomb of charge

Question 3

What is resistance?

Answer 3

Resistance is anything that slows the flow down. Unit : ohm

Question 4

What happens when there is a high potential difference?

Answer 4

There is a high current

Question 5

What will happen if there is a high resistance?

Answer 5

There will be a low current

Question 6

How do you work out charge?

Answer 6

Charge = current x time

Question 7

What unit is charge in?

Answer 7

Coulombs

Question 8

How do you work out energy transferred?

Answer 8

Energy transferred = charge moved x potential difference

Question 9

How to work out resistance?

Answer 9

Resistance = potential difference / current

Question 10

What does an ammeter do?

Answer 10

This measures the current (in amps) flowing through the component. It can be put anywhere in the main circuit

Question 11

What does a volt meter do?

Answer 11

This measures the potential difference across the component. It must be placed under parallel with the component under test

Question 12

What do linear components have on an iv graph?

Answer 12

A straight line

Question 13

What do non - linear components have on an iv graph?

Answer 13

A curved line

Question 14

How to work out the resistance on an iv graph?

Answer 14

The resistance will be the inverse of the gradient or 1/gradient. The steeper the graph the lower the resistance

Question 15

What is an ldr?

Answer 15

An ldr ( light dependent resistor) is a resistor that is dependent on the intensity of light. In bright light, resistance falls. In darkness, the resistance is highest

Question 16

What is a thermistor?

Answer 16

A thermistor is a temperature dependent resistor. In hot conditions, the resistance drops. In cool conditions, the resistance goes up

Question 17

Which way do electric field lines travel?

Answer 17

Positive to negative

Question 18

Which way do electric filed lines face?

Answer 18

At a right angle to the surface

Question 19

What do close filed lines represent?

Answer 19

A stronger electric field

Question 20

How do photocopiers work?

Answer 20

They use static electricity the copy images onto a charged plate before printing them

Question 21

How do electrostatic sprayers work?

Answer 21

Bikes and cars are painted using electrostatic paint sprayers. The spray gun is charged, which charges up small drops of paint, each drop repels all others, so you get a very fine, even layer of paint over the the bike or car

Question 22

How can static electricity be dangerous when refuelling a car?

Answer 22

A fuel flows out of a fuelling pipe, eg a aircraft or tanker, then static electricity can build up, this can easily cause a spark which can lead to an explosion

Question 23

What happens when electric charge builds up on an object?

Answer 23

The potential difference between the object and the earth increases, if the potential difference gets large enough, electrons can jump across the gap between the charged object and the earth

Question 24

What happens with 2 things with opposite electric charges?

Answer 24

They are attracted to each other

Question 25

What happens to 2 electric things with the same charge?

Answer 25

The repel each other

Question 26

What happens with insulating materials are rubbed toegther?

Answer 26

Negatively charged electrons will be scraped off one and dumped on the other, as the materials are insulators, these electrons are not free to move, this build up of charge is static electricity

Question 27

What is a series circuit?

Answer 27

In a series circuit, the different components are connected in a line, end to end. If you disconnect 1 component, the circuit is broken

Question 28

What is a parallel circuit?

Answer 28

In parallel circuits, each component is separately connected to the power, if you move or disconnect one of them it will hardly change the others at all

Question 29

What happens to the p.d. And the current in a series circuit?

Answer 29

Theres a bigger p.d when there are more cells in a series, e.g 2 batteries with 1.5 v supply 3 v. The current is equal everywhere I1 = I2 = I3

Question 30

What happens to the p.d and the current in a parallel circuit?

Answer 30

In a parallel circuit, the potential difference is the same across all components v1 = v2 = v3. Current is shared between branches. The total current flowing around the circuit is equal to the total of all the currents through the separate components. Itotal = i1 + i2

Question 31

What happens when you add a resistor in a series circuit?

Answer 31

The total resistance increases because by adding a resistor, the two resistors share the total p.d

Question 32

What happens when you add a resistor to a parallel circuit?

Answer 32

The total resistance decreases because, if you have 2 resistors in parallel, their total resistance is less than the resistance of the smallest of the 2 resistors

Question 33

How do you work out energy transferred?

Answer 33

Energy transferred = current x p.d x time

Question 34

How is energy transferred in a kettle?

Answer 34

The energy is electric which then transfers to the thermal energy of the kettle

Question 35

How do you work out power?

Answer 35

Power (w) = energy transferred / time

Question 36

How do you work out electrical power?

Answer 36

Electrical power = current x p.d

Question 37

What is an a.c?

Answer 37

In a.c supplies the movement of the charges is constantly changing direction. Alternating currents are produced by alternating voltages

Question 38

What is a d.c?

Answer 38

In direct current the movement of the charges is only in 1 direction. Its created by a direct voltage

Question 39

What is the live wire?

Answer 39

Brown, the live wire carries the voltage. Goes up to 230 v

Question 40

What is the neutral wire?

Answer 40

Blue the neutral wire completes the circuit, electricity normally flows in through the live and out through the neutral wire. The neutral wire is always at 0v

Question 41

What is the earth wire?

Answer 41

Green and yellow, the earth wire is for safety and protecting the wiring. It carries the current away if something goes wrong and stops the appliance casing going live. Its also at 0v

Question 42

What is an electric shock?

Answer 42

Your body is at 0v, this means that if you touch the live wire, a potential difference is produced across your body and a current flows through you. This causes a large electric shock which could kill you

Question 43

How does a fuse work?

Answer 43

When a voltage gets too high, the fuse wire melts so that no more electricity can come through

Question 44

What is a circuit breaker?

Answer 44

Instead of a fuse wire, the circuit breaker may just trip something to the power of. Circuit breakers turn off quicker than fuses do and can be reset, but are more expensive