5 Electricity and Magnetism

Question 1

Current SI units

Answer 1

Amperes (A)

Question 2

Charge SI units

Answer 2

Coulombs (C)

Question 3

Potential Difference SI units

Answer 3

Volts (V)

Question 4

Measures Current

Answer 4

Ammeter

Question 5

Measures Potential Difference

Answer 5

Voltmeter

Question 6

Methods of magnetisation (3)

Answer 6

Stroking with a magnet, use of direct current in a coil, and hammering in a magnetic field

Question 7

Unlike charges …

Answer 7

Attract

Question 8

Like charges …

Answer 8

Repel

Question 9

Charging a body involves …

Answer 9

The addition or removal of electrons

Question 10

Electric field

Answer 10

A region in which an electric charge experiences a force

Question 11

Current

Answer 11

The rate of flow of charge

Question 12

Current in metals is due to …

Answer 12

A flow of electrons

Question 13

Electromotive force SI units

Answer 13

Volts (V)

Question 14

Electromotive force

Answer 14

The energy supplied by a source in driving
charge around a complete circuit

Question 15

Equation for Current

Answer 15

I = Q / t

Question 16

Equation for Resistance

Answer 16

R = V / I

Question 17

Resistance SI units

Answer 17

Ohms (Ω)

Question 18

Electrical Conductors

Answer 18

Conduct electricity, let electrons pass through them, eg. metals, graphite

Question 19

Electrical Insulators

Answer 19

Hardly conduct, electrons are tightly held to atoms but can be transferred by rubbing, eg. glass, rubber, plastic, dry air

Question 20

Electrical Semi-conductors

Answer 20

Poor conductors when cold, but much better when warm, eg. silicon, germanium

Question 21

Sum of potential differences across the components is equal to the …

Answer 21

Potential difference across the battery

Question 22

Direction of an Electric Field

Answer 22

Direction of the force on a positive charge in the electric field

Question 23

Magnetic elements (3)

Answer 23

Iron, cobalt, nickel

Question 24

Direction of a Magnetic Field

Answer 24

North to South

Question 25

Alternating Current (a.c.)

Answer 25

Electrons flow in one direction, then in the opposite direction, back and forth

Question 26

Direct Current (d.c.)

Answer 26

Electrons flow continuously in one direction

Question 27

Uncharged objects have ...

Answer 27

Both positive and negative charges

Question 28

Production of electrostatic charges

Answer 28

Build up of electrons

Question 29

Build up of electrons occurs in ...

Answer 29

Insulators, not conductors

Question 30

Magnetic field strength decreases as ...

Answer 30

Distance increases

Question 31

Perspex rod is rubbed

Answer 31

Electrons exit

Question 32

Polythene rod is rubbed

Answer 32

Poly = many, so gains electrons

Question 33

Describe the relationship between resistance, length and area

Answer 33

R ∝ l R ∝ 1/a R ∝ l/a

Question 34

Equation relating resistivity, resistance, length and area

Answer 34

P = (R x a)/l

Question 35

For 2 identical resistors connected in parallel, the effective resistance is ...

Answer 35

R/2 = half of either resistor by itself

Question 36

Series circuit (current)

Answer 36

I₁ = I₂ = I₃

Question 37

Series circuit (potential difference)

Answer 37

Vₛ = V₁ + V₂

Question 38

Series circuit (resistance)

Answer 38

Rₜ = R₁ +R₂

Question 39

Parallel circuit (current)

Answer 39

I₁ = I₂ + I₃ = I₄

Question 40

Parallel circuit (potential difference)

Answer 40

Vₛ = V₁ = V₂

Question 41

Parallel circuit (resistance)

Answer 41

1/Rₜ = 1/R₁ + 1/R₂

Question 42

Thermistor effect of temperature on resistance

Answer 42

Temperature increases, resistance decreases

Question 43

Light dependent resistor (LDR) effect of light on resistance

Answer 43

Light increases, resistance decreases