P3

Question 1

What is electric charge?

Answer 1

A property of matter that can be positive or negative.

Question 2

When is a body neutral?

Answer 2

When it has equal positive and negative charges.

Question 3

What happens with like and unlike charges?

Answer 3

Like charges repel; opposite charges attract.

Question 4

What are insulators?

Answer 4

Materials where charged particles are fixed and cannot flow—do not conduct charge.

Question 5

What are conductors?

Answer 5

Materials with delocalised charged particles that can flow—can conduct charge.

Question 6

What happens when two insulators are rubbed together?

Answer 6

Electrons transfer—one object gains electrons (negative), the other loses (positive).

Question 7

Why don’t conductors build static charge when rubbed?

Answer 7

Electrons flow in and out, cancelling out charge.

Question 8

What causes a spark?

Answer 8

When enough charge builds up and the objects are close but not touching p.

Question 9

What is electrostatic force?

Answer 9

A non-contact attractive or repulsive force between charge

Question 10

What affects the strength of electrostatic force?

Answer 10

Greater charge and smaller separation (inverse square law)

Question 11

What happens when a charged object is near a neutral one?

Answer 11

It induces a charge in the neutral object, attracting it.

Question 12

Give an example of electrostatic attraction in real life.

Answer 12

stream of water bends toward a charged object (like a balloon)

Question 13

What direction do electric field lines point?

Answer 13

Away from positive, towards negative charges.

Question 14

What does more field lines indicate?

Answer 14

A stronger charge and stronger force.

Question 15

What are the conditions for current to flow?

Answer 15

A closed circuit and a source of potential difference.

Question 16

What pushes current through resistance?

Answer 16

Potential difference (voltage).

Question 17

What is the formula for charge?

Answer 17

Q = I × t (charge = current × time)

Question 18

Is current the same in a closed loop?

Answer 18

Yes—same at any point in a single, closed circuit.

Question 19

What is potential difference (p.d)?

Answer 19

The energy transferred per unit charge, measured in volts (V).

Question 20

How is p.d. measured?

Answer 20

Using a voltmeter placed in parallel across a component.

Question 21

What is electric current?

Answer 21

The rate of flow of charge (electrons), measured in amperes (A).

Question 22

How is current measured

Answer 22

With an ammeter placed in series in the circuit.

Question 23

What is a series circuit?

Answer 23

A closed circuit with only one path for current—same current everywhere.

Question 24

What is a parallel circuit?

Answer 24

A branched circuit—current splits into paths, but voltage stays the same across each branch.

Question 25

What is the formula linking voltage, current, and resistance?

Answer 25

V = I × R (Voltage = Current × Resistance)

Question 26

What does a linear I-V graph indicate?

Answer 26

Constant resistance. - ohm’s law if followed

Question 27

What causes a non-linear I-V graph?

Answer 27

Changing resistance due to heat, current, or wire length.

Question 28

What happens to resistance as current increases?

Answer 28

Electrons have more energy → collide with atoms → atoms vibrate more → resistance increases. - current flow is reduced

Question 29

What happens to resistance with increasing temperature in normal wires?

Answer 29

It increases due to increased atomic vibrations.

Question 30

What happens to resistance in a thermistor as temperature increases?

Answer 30

Resistance decreases — useful in thermostats.

Question 31

How does wire length affect resistance?

Answer 31

Longer wire = more resistance; current decreases electrons face more obstacles, have to pass through more atoms

Question 32

How does cross-sectional area affect resistance?

Answer 32

Thinner wire = higher resistance; less space for electrons to flow.

Question 33

What happens to resistance in an LDR as light increases?

Answer 33

Resistance decreases — highest resistance when dark.

Question 34

What is the function of a diode?

Answer 34

Allows current to flow in one direction only; very high resistance in the other direction.

Question 35

What is a use of a diode?

Answer 35

Converting AC to DC.

Question 36

What must you avoid during electrical experiments?

Answer 36

Overheating components — let them cool between readings.

Question 37

How do you test resistance with different wires?

Answer 37

Use wires (1Ω–10Ω), connect to 2–12V DC, measure current and voltage, and plot I-V graph.

Question 38

What is important about other wires in the circuit when measuring resistance?

Answer 38

They should have negligible resistance

Question 39

How do you test a filament lamp?

Answer 39

Vary voltage (2–12V), measure current, plot I-V graph — shows non-linear resistance.

Question 40

How do you test a diode?

Answer 40

Measure current for positive and negative voltages (e.g. 1 to -4V), plot I-V graph - shows current only flows in one direction

Question 41

How do you test an LDR?

Answer 41

Shine light at different distances (10–50cm), measure current/resistance, and plot resistance vs light intensity.

Question 42

How do you test a thermistor?

Answer 42

Place in water from 0ºC–60ºC, measure current, calculate resistance, and plot resistance vs temperature.

Question 43

What happens to current in a series circuit?

Answer 43

It flows through all components equally.

Question 44

What is the total resistance in a series circuit?

Answer 44

The sum of all component resistances.

Question 45

Why is total resistance in series greater?

Answer 45

The charge must push through all items (resistors) .

Question 46

How are components connected in a parallel circuit?

Answer 46

Each component is connected separately to the power supply.

Question 47

What happens to total resistance in a parallel circuit?

Answer 47

It is less than the resistance of the smallest individual resistor.

Question 48

Why does resistance decrease in parallel circuits?

Answer 48

Charge splits across multiple paths, reducing overall resistance.

Question 49

What is the formula for electrical power?

Answer 49

Power = Voltage × Current → P = V × I

Question 50

What is the alternate formula for power using resistance?

Answer 50

P = I² × R

Question 51

What is the unit of power?

Answer 51

Watts (W)

Question 52

What is the formula for energy transferred (using charge)?

Answer 52

Energy = Charge × Voltage → E = Q × V

Question 53

What is the formula for energy using power and time?

Answer 53

Energy = Power × Time → E = P × t

Question 54

What are the units of energy?

Answer 54

Joules (J)

Question 55

How to calculate resistance in a parallel circuit?

Answer 55

as the sum of reciprocals of resistance 1/R(total) = 1/R(1) + 1/R(2) + …

Question 56

What is the spark?

Answer 56

A discharge where charge jumps through the air to balance out.