Electromagnetism

Question 1

Coulomb’s Law

Answer 1

Describes the force of attraction (or repulsion) between two charges.

Question 2

Electric Field

Answer 2

The region that surrounds electrically charged particles in which a force is
exerted on other electrically charged particles.

Question 3

Electrostatic shielding

Answer 3

When devices which might be affected by an electric field are enclosed in a
conductive material so that the electric field inside is zero.

Question 4

Electric field strength

Answer 4

The electrical force per unit positive charge.

Question 5

Electrostatic potential

Answer 5

The work done in moving unit positive charge from infinity to a certain point.

Question 6

Electronvolt (eV)

Answer 6

A unit of energy, often used in high-energy particle physics.
1 eV is equivalent to 1.6x10-19 J.

Question 7

Ferromagnetic Material

Answer 7

A material which can become permanently magnetised. Examples include iron,
steel, cobalt and nickel.

Question 8

Magnetic field

Answer 8

A region of space around a magnet where another magnet will experience a
force.

Question 9

Solenoid

Answer 9

A current-carrying wire wrapped around a soft iron core to form a coil.

Question 10

Magnetic Induction

Answer 10

The strength of a magnetic field at a point.

Question 11

Fleming’s right hand rule

Answer 11

Used to determine the direction of the force on a current-carrying wire, or
moving charge, in a magnetic field.

Question 12

Pitch

Answer 12

The distance between adjacent loops in the helix after one period when a
charged particle enters a magnetic field at an angle.

Question 13

Capacitor

Answer 13

An electronic device which stores charge and therefore energy in electrical
circuits. They are often used in circuits that require a time delay before
releasing energy.

Question 14

RC circuit

Answer 14

A circuit containing both a resistor and capacitor.

Question 15

Time Constant

Answer 15

If the capacitor is charging, it is the time taken to increase the charge stored to
63% of the difference between initial charge and full charge.
If the capacitor is discharging, it is the time taken for the capacitor to discharge
to 37% of its initial charge.

Question 16

Resistance

Answer 16

Where a device will oppose current flowing through it because of a physical
property of the device.

Question 17

Reactance

Answer 17

Where a device will oppose current flowing through it because of a phenomena
produced when the device is working.

Question 18

Capacitive Reactance

Answer 18

The opposition of a capacitor to changing current (i.e. a.c. current).

Question 19

Electromagnetic Induction

Answer 19

When a moving or varying magnetic field cuts a conductor to create an
electromotive force (e.m.f.) across it.
OR
When a conductor is moved perpendicular to a magnetic field it will generate
an e.m.f. across the conductor.

Question 20

Inductor

Answer 20

A coil of wire which is often wrapped around an iron core.
Without an iron core, it is called an air cored inductor.
With an iron core, it is called an iron cored inductor.

Question 21

Back EMF

Answer 21

Produced when a magnetic field is generated around the coil when an inductor
is placed in a circuit in which the current is changing.

Question 22

Lenz’s Law

Answer 22

The induced e.m.f. always opposes the change in current which causes it

Question 23

Self-induced EMF

Answer 23

When a coil induces an e.m.f. in itself due to its own changing current.

Question 24

Inductance

Answer 24

A property of an inductor itself. It depends on its design.

Question 25

Inductive Reactance

Answer 25

The opposition of an inductor to changing current (i.e. a.c. current)

Question 26

Electromagnetic Radiation

Answer 26

Exhibits wave properties as it transfers energy through space.
It has both electric and magnetic field components which oscillate in phase,
perpendicular to each other and to the direction of energy propagation.
All EM radiation travels at the speed of light in a vacuum (3x108 ms-1
)