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Year 8- Science > Electricity And Magnetism > Flashcards

Electricity And Magnetism Flashcards

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1
Q

What are the two types of electric charge?

A

Positive charge (+) and negative charge (-)

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2
Q

What do charges do that are similar to magnets?

A

Charges attract and repel each other, like magnets do

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3
Q

What charges repel each other and what charges attract each other?

A

Positive charges repel positive charges
Negative charges repel negative charges
Positive charges attract negative charges

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4
Q

What are the small things that everything is made from?

A

Atoms

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5
Q

What three things is an atom made of?

A

Protons, which have a positive charge
Electrons, which have a negative charge
Neutrons, which have no charge

An atom contains equal numbers of protons and electrons. Overall an atom has no charge-it is neutral

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6
Q

What is charge?

A

Charge is a property of a particle or object, just like mass. Each object either has an equal, positive or negative charge.

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7
Q

How do objects get a positive or negative charge?

A

For example-when you rub a balloon on your jumper some electrons are transferred from the jumper to the balloon. The balloon bow has an overall negative charge.your jumper has an overall positive charge. They will attract. The balloon is made of rubber. The electrons stay on the balloon.

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8
Q

Which of the three thing that make up an atom can transfer to other objects?

A

Electrons are the only part of the atom that can transfer from an object to another object. The protons and neutrons do not move from the atom.

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9
Q

How does a thundercloud produce current?

A

In a thundercloud, air moves around, producing regions that have a positive or negative charge. Electrons jump from one charged area to another and this produces a big current, which quickly heats the air. You see lightning and hear thunder.

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10
Q

What is an electric field?

A

There is an electric field around a charge, just as there is a gravitational field around a mass. Of you put a charged object in an electric field, a force will act on it.

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11
Q

What is current?

A

When you complete a circuit, charged particles or charges move in the metal wires. The current is the amount of charge flowing per second past a point.

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12
Q

What is a switch used for in a circuit?

A

The switch opens and closes a gap in the circuit. You need to close the gap and make a complete circuit for a current to flow.

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13
Q

What can you measure the current of a circuit with?

A

You can measure the current with an ammeter.

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14
Q

What is current measured in?

A

Current is measured in amperes or amps. The symbol for amps is A.

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15
Q

What pushes the charge around a circuit?

A

The cell or battery pushes charges around the circuit. The battery does not produce the charges that move. They were already there in the wires. In a metal the charged particles that move are electrons.

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16
Q

What are circuit symbols?

A

You can build circuits using components such as batteries, bulbs and motors. It would take a long time to draw a picture of each circuit so you can use circuit symbols instead.

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17
Q

What must you make sure to do with the different end of the batteries or cells in a circuit?

A

You must make sure that you connect the cells or batteries the right way round or they will not work.

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18
Q

What is potential difference?

A

The cell or battery provides the push to make charges move. The push is called a potential difference, or p.d for short.

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19
Q

What does the potential,difference across a cell tell you?

A

The potential difference across a cell tells you about the size of the force on the charges. It also tells you how much energy can be transferred to the components in the circuit by the charges.

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20
Q

What can you use to measure the amount of potential difference?

A

You measure potential difference using a voltmeter.

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21
Q

What unit potential difference measured in?

A

The potential difference is measured in volts. The symbol for volts is V.

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22
Q

What is the rating of a cell?

A

You can measure the potential difference of a cell by connecting a voltmeter across it. This is also called the rating.

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23
Q

Do other components in a circuit also have a rating?

A

Yes, circuit components such as bulbs also have a rating.

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24
Q

What are the two types of circuits?

A

Series and parallel circuits.

25
Q

What is a series circuit?

A

The old type of Christmas lights were connected in series. All the bulbs formed one loop, including the battery and the switch. This meant that if one light broke then all of the lights didn’t work.

26
Q

What is a parallel circuit?

A

There is another type of circuit called a parallel circuit. In a parallel circuit there is more than one lop or branch. Parallel circuits are sometimes called ‘branching circuits’. This means that if one light broke then the rest lf the lights would still work.

27
Q

What happens to the current in a series circuit?

A

In a series circuit the current is the same everywhere. If you add components to a series circuit the current will get smaller.

28
Q

What happens to the current in a parallel circuit?

A

The current in all branches of a parallel circuit add together to make the total current. If you add another branch to a parallel circuit the current in the other branches stays the same but the total current increases.

29
Q

What happens to the potential difference in a series circuit?

A

The potential difference across each component adds up to the potential difference across the battery.

30
Q

What happens to the potential difference in a parallel circuit?

A

The potential difference across each component is the same as the potential difference across the battery.

31
Q

State what is meant by resistance?

A

Components do different jobs in an electric circuit. Each circuit component has a different resistance. This tells you how easy or difficult it is for the charges to pass through the component.

32
Q

What is resistance measure in?

A

Resistance is measured in ohms, which has the symbol Ω. Ω is a letter from the Greek alphabet and is the omega sign.

33
Q

How do you calculate the current of a circuit?

A

Potential difference (V)

Current (A)=

   Resistance (Ω)
34
Q

What is the equation to calculate the resistance of a component?

A

Potential difference (V)

Resistance (Ω)=

          Current (A)
35
Q

What happens inside a wire?

A

The charges that move in a wire are electrons. Inside a wire the moving electrons collide with the atoms of wire creating resistance. They transfer energy, and the wire gets hot.

36
Q

Why are metals good conductors?

A

They have a low resistance because they contain lots of electrons that can move.

37
Q

Why are plastics good insulators?

A

Materials like plastics do not have many electrons that are free to move. The resistance of plastics is very high. Insulators have a high resistance just like plastic.

38
Q

What are the two poles of a magnet?

A

The north and south pole

39
Q

What poles attract and what poles repel?

A

North pole repel north poles
South poles repel south poles
North poles attract south poles

40
Q

What are materials called that are attracted to magnets?

A

Only certain materials are attracted to a magnet. They are called magnetic materials.

41
Q

What is a magnetic field?

A

In an electric field there is a force in a charge. In a magnetic field there is a force on a magnet or a magnetic material.

42
Q

What two ways can you find out the shape pf a magnetic field?

A

Using ‘plotting compasses’ and placing a dot and joining them where the compasses point to.
Using iron filings which creat a shape and lines up with the magnetic field of a magnet.

43
Q

What way do the magnetic field lines head towards?

A

The lines go from the north pole to the south pole of the magnet.

44
Q

What does it mean if the magnetic field lines are closer together or further away?

A

If the magnetic field lines are closer together this shows that the magnetic field is stronger. If it is further away then it is weaker.

45
Q

What is a permanent magnet?

A

A permanent magnet is a magnet that has its own magnetic field.

46
Q

What is the Earth’s magnetic field?

A

If you hang a magnet up it will line up in a direction pointing north to south. This is because it is in the magnetic field of the Earth. TheEarth behaves as if there is a huge bar magnet inside it. Physics are not sure what produces the Earth’s magnetic field.

47
Q

What is an electromagnet?

A

a soft metal core made into a magnet by the passage of electric current through a coil surrounding it.

48
Q

Are you able to turn an electromagnet on and off?

A

Yes, you can turn an electromagnet on and off by turning the current flowing through the wire on and off. The magnetic field is only produced when the current is flowing in the wire.

49
Q

What is a core of an electromagnet?

A

Electromagnets usually have a magnetic material in the centre of the coil, called a core. This makes the electromagnet much stronger. They are usually made of iron.

50
Q

What is the wire in an electromagnet?

A

The wire in an electromagnet is the part were the current flows through. The wire raps round a core and creates coils.

51
Q

What are the 3 factors that increase the strength of an electromagnet?

A

1) more coils of wire
2) higher current (in amps)
3) include a core e.g iron

52
Q

What are the two main differences between permanent magnets and electromagnets?

A

1) you can turn an electromagnet on and off

2) you can make electromagnets that are much stringer than permanent magnets

53
Q

What do some trains use electromagnets for?

A

Some trains use magnetic levitation. This means the train is lifted up using magnets that repel each other.

54
Q

What is a relay?

A

A relay uses a small current in one circuit to operate a switch in another circuit. When the switch is closed the coil becomes and electromagnet.

55
Q

How do you start a car?

A

The driver switches on the circuit in the battery to start the car. They can do this safely using an electromagnet switch.

56
Q

Can you use an electromagnet to lift heavy objects?

A

Yes because of its magnetic strength. It is used to move cars in a scrapyard.

57
Q

Can an electromagnet be used to separate metals that are attracted to magnets and metals that are not?

A

Yes

58
Q

Where are electromagnets used?

A

Maglev trains, hospitals and cars.

Year 8- Science (6 decks)

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