9Ja Magnetic Fields
9Jb Static Electricity
9Jc Current and Electricity
9Jd Resistance
9Je Electromagnets
100
2 like poles of a magnet will ______ each other.
repel
100
What type of charge does an electron have?
Negative
100
What is electric current measured in, and what letter is used to represent current in an equation?
Amperes/Amps. Letter: I
100
What is the name and symbol for what resistance is measured in?
Ohms (omega)
100
What is produced when an electric current flows through a wire?
Magnetic field is produced around the wire.
200
Draw a magnetic field around a bar magnet. Include arrows to show which direction the lines flow.
200
Draw a diagram of an atom. Label the nucleus, protons, neutrons, and electrons.
200
What is the name of the piece of equipment used to measure current?
Ammeter
200
A bulb is connected to a power supply of 12V. The current flowing through the bulb is 2A. Calculate the resistance of the bulb. Include units.
R = V/I
R = 12/2 = 6 ohms.
200
What is an electromagnet?
Magnet made by passing a current through a coil of wire
300
Why are the magnetic field lines closer together near the poles of a magnet?
Magnetic field is stronger at the poles
300
__________ causes e___________ to move from one object to another.
Friction, electrons
300
Give the symbols used for:
Ammeter
Voltmeter
Battery/cell
Bulb
300
Name 2 factors that affect the resistance of a wire.
Length, thickness, material type
300
Name 2 ways to make an electromagnet stronger.
Increase current/voltage, add more coils of wire, add an iron core
400
Why is the Earth like a big bar magnet?
Its core is made of iron and nickel that is constantly spinning
400
The gain or loss of electrons can only happen if the object is an electrical ____________.
insulator
400
Draw a series circuit and a parallel circuit.
acceptable drawing
400
What is the relationship between the length of a wire and the amount of resistance?
greater length of wire = more resistance
400
Why does an iron core increase the strength of an electromagnet?
Iron becomes magnetised and concentrates the magnetic field.
500
Explain why a compass needle always points north when placed in Earth's magnetic field
Earth is like a giant magnet. The compass needle is a small magnet, so it aligns with Earth's magnetic field and points north.
Also: Earth's magnetic south pole is at the geographical north pole, so the compass (N) is attracted to that.
500
Why can't static charge build up on conductors?
Electrons move too easily so the charge disappears.
500
Assuming resistance stays the same, explain why increasing the voltage will increase the current.
A higher voltage pushes the charges with more energy, causing more current to flow.
500
Why does the resistance change with the length of wire?
Electrons collide with atoms in the wire, so a longer wire causes more collisions over a longer distance which slows the current.
500
Explain 1 advantage and 1 disadvantage of using an electromagnet over a permanent magnet
A: can be switched on and off, can have its strength changed, can change the direction
D: needs an electric current to work