P5 - Electricity and magnetism Flashcards
What is the law of magnetic poles? [2]
Like poles repel, unlike poles attract
What happens to a piece of unmagnetised magnetic material when it touches or is bought near to the pole of a permanent magnet? [2]
It becomes an induced magnet and will be attracted to the magnet
Describe temporary magnets [2]
These are made of soft iron and lost their magnetism easily
Describe permanent magnets [2]
These are made of steel and retain their magnetism
Name the three elements that are magnetic [3]
Iron, cobalt and nickel
Why is steel magnetic? [1]
Because it contains iron
What is a magnetic field? [1]
The space around a magnet where it produces a magnetic force
What is the direction of magnetic field lines?
From North to South
Where on a bar magnet is the magnetic field strongest? [2]
Near the poles (the magnetic field lines are closer)
Describe how to plot the magnetic field pattern of a bar magnet [3]
- Place a plotting compass near the pole of a magnet and mark the direction the compass points. 2. Move the compass around the bar magnet marking where the compass points. 3. Join the points up and add an arrow pointing from the north pole to the south pole.
Like charges… [1]
repel
Unlike charges… [1]
attract
How can an object be charged? [2]
Removal or addition of electrons
What is an electric field? [1]
A region in which an electric charge experiences a force
Describe a conductor and give an example [2]
Something that lets electrons pass through e.g. metals / graphite
Describe why an insulator does not allow electrons to pass through easily and give an example [2]
Electrons are tightly held to atoms are are not free to move but can be transferred by rubbing e.g. plastics / glass
Describe a semi conductor and give an example
Poor conductors when cold but better when warm e.g. Silicon / Germanium
What is the unit of charge? [1]
Coulomb
Define current [1]
The flow of charge past a point per unit time
What is the equation that relates current (I), charge (Q) and time(t)? [1]
I = Q/t
What direction is conventional current? [1]
Positive to negative
What direction is the flow of free electrons? [1]
Negative to positive
What is used to measure current and how is this connected in a circuit? [2]
An ammeter connected in series
Define electromotive force (e.m.f) [1]
The electrical work done by a source in moving unit charge around a complete circuit
Define potential difference (p.d) [1]
The work done by a unit charge passing through a component
What other word is used for potential difference? [1]
Voltage
What are the units of electromotive force and potential difference? [1]
Volts
What is use to measure potential difference and how is this connected in a circuit? [2]
Voltmeter connected in parallel
