P2 Electricity and magnetism pages 122-138 yr 8 Flashcards
What do doctors use to help keep a baby alive and how?
Doctors use an incubator to help keep a premature alive. an electric current flows through a heater that keeps the baby warm.
What is current?
The current is the amount of charge flowing per second.
What happens when you complete a circuit?
When you complete a circuit, charged particles or charges move in metal wires.
What do need to do for the current to flow in a complete circuit?
When you press the switch on a torch the light comes on. 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.
When people talk about electricity what do they usually mean?
When people talk about ‘electricity they usually mean ‘electric current.’
How do you measure current?
You can measure current using an ammeter
What is current measured in?
Current is measured in amps.
What is amps shortened for?
Amps is shortened for amperes.
What is the symbol for amps?
Give an example on how to use the symbol.
The symbol for amps is ‘A’ e.g. the current in the circuit 0.4 A.
Where do the charges come from?
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.
How do you can build circuits? Using what?
You can build circuits using components such as batteries, bulbs and motors.
Why do we use symbols instead of drawing each diagram as a picture?
It would take a long time to draw a picture of each circuit so you can use circuit symbols instead.
What is a cell?
A cell is another word for a battery.
What could be a reason for the circuit not working?
The cells might not be connected in the right way round.
What do doctors use to start someone’s heart if it stops?
A doctor can use a defibrillator to start someone’s heart if it stops.
What can defibrillators produce?
Defibrillators produce a large potential difference (sometimes called voltage), much bigger than a battery can produce.
What does p.d. stand for and what is it?
The cell or battery provides the push to make the charges move. The push is called a potential difference which is what p.d. stands for.
What can potential difference tell you about the force on charges?
The potential difference across a cell tells you about the size of the force on the charges.
What does potential difference also tell you?
The potential difference also tells you how much the energy can be transferred to the components in the circuit by the charges.
How does a potato produce a potential difference?
In a potato cell a chemical reaction between the metals and the potato produces a potential difference.
How do you measure potential difference?
You measure potential difference by using a voltmeter which can be shortened to volts.
What is the symbol for volts?
Give example of it can be used.
The symbol for volts is ‘V’. For example, the potential difference across the cell is 6V.
What is a rating?
You can measure the potential difference of a cell by connecting a voltmeter across it. This is also called the ratting.
What can you measure the potential difference with?
You can measure the potential difference across a component in a circuit using a voltmeter.
What is a better word to sue instead of voltage?
Sometimes people talk about the voltage of a cell or a battery. It is better to talk about potential difference.
How can you think of a battery?
You can think of the battery lifting up the charges.
What is the difference between a parallel and series circuit?
In a series circuit there is only one loop whereas in a parallel circuit there is mor than one loop.
Why are parallel circuits very useful?
Parallel circuits are very useful because if one bulb breaks, the other lights stay on. Each bulb is independent of the others.
How can control each lamp separately?
You can control each lamp separately in a parallel circuit by adding a switch to each branch.
What is the current in a series circuit?
In any circuit that is connected in series anywhere where you place the ammeter the current will have the same reading.
What will happen if you add components to a series circuit?
If you add components to a series circuit the current will get smaller.
What is the current in a parallel circuit?
In a parallel circuit each branch has the same current.
What happens if you add another branch to a parallel circuit?
If you add another branch to a parallel circuit the current in the other branches stay the same but the total current increases.
How can you use a rope to think of a series circuit?
You can use a rope model when you are thinking about different types of circuit. In the rope model:
The rope moves at the same speed everywhere.
As more people hold the rope, the rope moves more slowly.
How can you use a rope to show how parallel circuits work?
There are more loops of rope.
All the loops are driven by the same ‘battery’ person
What happens to the potential difference in a series circuit?
The potential difference across each component adds up to the potential difference across the battery.
What happens to the potential difference in a parallel circuit?
The potential difference across each component is the same as the potential difference across the battery.
What does each component have in a circuit?
Each circuit component has a different resistance.
What does resistance tell us?
The resistance tells us how easy or difficult it is for the charges to pass through the component.
What is resistance measured in?
Resistance is measured in ohms.
What is the symbol for ohms?
The symbol for ohms
What does the current depend on?
The current depends on the push of the battery and also the resistance of the component.
What equation do you use to calculate current?
Current(A) =potential difference(V)
divided by resistance
What equation can you use to calculate the resistance of a component?
Resistance =potential difference (V)
Current (A)
What happens inside a wire?
Inside a wire the moving electrons collide with the atoms of the wire. They transfer energy, and the wire gets hot.
Name a liquid that is magnetic.
Ferrofluid is a special liquid that is magnetic.
What does a magnet have?
A magnet has a north pole and a south pole
What do north poles _______ north poles?
Repel
What do south poles _______ South poles
Repel
What do South poles _______ North poles?
Attract
What are the materials attracted to a magnet called?
Only certain materials are attracted to a magnet. They are called magnetic materials.
Give some examples of some metals.
Iron is a magnetic material, and so is steel because steel contains iron. Cobalt and nickel are also magnetic.
What is a magnetic field?
In an electric field there is a force on a charge. In a magnetic field there is a force on a magnet or a magnetic material.
What are the two ways that you can find out the shape of a magnetic field?
Using plotting compasses, using iron filings.
What does a wire with an electric current flowing through it have?
A wire with an electric current flowing through it has a magnetic field around it.
How can you investigate the field?
You can investigate the field with a plotting compass.
Describe the strength of a magnetic field with a single loop.
The magnetic filed around a single loop isn’t very strong.
What will make the magnetic much stronger?
If you put lots of loops together to make a coil the field is much stronger.
What is an electromagnet?
Putting lots of loops close together forms an electromagnet because it has a strong magnetic field.
What is the shape of the magnetic field like?
The shape of the magnetic field is just like the shape of the magnetic field around a bar magnet.
How can you turn an electromagnet off and on?
You can turn an electromagnet off and on by switching the current off and on.
When is the magnetic field produced?
The magnetic field is only produced when the current is flowing in the wire.
What do electromagnets usually have in the centre of the coil?
Electromagnets usually have a magnetic material in the centre of the coil, called a core.
What does the core do to the electromagnet?
The core makes the electromagnet much stronger.
What are most core made of?
Most cores are made of iron.
Is iron easy to magnetise?
Yes iron is easy to magnetise but it loses its magnetism easily.
Describe the magnetism of steel.
Steel is hard to magnetise but keeps its magnetism.
What would happen if you had a steel core?
If you had a steel core in an electromagnet you could not turn the electromagnet off, because the steel would still be magnetic.
How can you make electromagnets stronger?
The strength of an electromagnet depends on:
The number of turns, or loops, on the coil. More tuns of the wire will make a stronger electromagnet.
The current flowing in the wire. More current flowing in the wire will make a stronger electromagnet.
The type of core. Using a magnetic material in the core will make a stronger electromagnet.
What are the two main differences between a permanent magnet and an electromagnet?
There are two main differences between permanent magnets and electromagnets.
You can turn an electromagnet on and off.
You can make electromagnets that are much stronger than permanent magnets.
What is one difference between an electromagnet and a bar magnet?
Electromagnets need electricity, but bar magnets do not. Both have fields.
Where are the field lines most concentrated around a bar magnet?
At both poles.
The arrow on magnetic field lines shows them flowing in which direction?
From North to South
What is an electromagnet?
A current flowing in a coil of wire acts like a magnet.
