Series & Parallel Circuits (OCR GCSE Physics A (Gateway)): Flashcards

False.

Connecting resistors in parallel gives a total resistance less than either individual resistance, because each resistor provides an extra path for charge to flow.

Each additional resistor in parallel creates an extra path for charge to flow. More paths means more charge flows overall, so the total resistance decreases.

Three resistors of 10 Ω, 20 Ω and 30 Ω are connected in series. The total resistance is 60 Ω.

Complete the table to compare resistors in series and parallel.

True.

In a series circuit, the power supply voltage is shared between the components, so the voltages across the individual resistors add up to the supply voltage.

Using R = R1 + R2:

R = 15 + 25 = 40 Ω

The total resistance of the series combination is 40 Ω.

The aim is to investigate and compare series and parallel circuits by measuring voltage and current for different arrangements of resistors and filament lamps.

The independent variable is potential difference (V). The dependent variable is current (I). Resistance is calculated from each pair of readings.

True.

For each arrangement, resistance is calculated using R = V / I, where V is the voltage reading and I is the current reading.

1. Start with a single resistor in series with a cell.

2. Add a second resistor in series.

3. Rearrange the two resistors in parallel.

4. Replace the resistors with a filament lamp and repeat.

In the PAG, the power supply should be disconnected between readings to prevent the components heating up too much.

Systematic: the voltmeter or ammeter may have a zero error if not started from zero. Random: the temperature of components changes during the experiment, altering their resistance.

False.

In parallel, the total resistance is less than either individual resistor — and less than the series total — because charge has more paths to flow through.

Complete the table of safety precautions for the series/parallel circuits PAG.

In a series circuit, the current is the same at all points around the loop — it does not split.

In a parallel circuit, the current splits at junctions. The total current from the supply equals the sum of the currents in each branch.

True.

In a parallel circuit, each branch is connected directly across the supply, so the potential difference across every branch equals the supply voltage.

In a series circuit, the supply voltage is shared between the components. In a parallel circuit, every component receives the full supply voltage.

In a parallel circuit, the current flowing into a junction must equal the current flowing out of the junction.

Using conservation of current at the junction:

current in = current out

10 A = 6 A + A2

A2 = 4 A

False.

In a series circuit, the supply potential difference is shared between the components, not equal to the supply voltage for each one.

Complete the comparison table for series and parallel circuits.

A voltmeter is a measuring instrument connected in parallel with a component to measure its potential difference.

False.

An ammeter is always connected in series with the components in a circuit, not in parallel.

The variable resistor controls the current flowing through the component, allowing different values of current to be tested.

To investigate resistance, the voltmeter is connected in parallel with the component, and the ammeter is connected in series with the circuit.

An LDR (light-dependent resistor) is a component whose resistance decreases as light intensity increases.

Resistance is calculated by dividing the measured potential difference by the measured current, using R = V ÷ I.

Complete the table to show how each meter is connected in a resistance investigation circuit.

True.

A thermistor is a component whose resistance decreases as temperature increases.

A thermistor is a component whose resistance decreases as temperature increases.

You wait to allow the LDR or thermistor time to react to the change in light intensity or temperature before the readings are taken.

Electrical power is the rate of energy transfer, measured in watts (W), where 1 W = 1 joule per second.

False.

The unit of electrical power is the watt (W), not the joule. The joule is the unit of energy.

The power of an electrical component depends on the potential difference (voltage) across it and the current flowing through it.

Power is defined as the rate of energy transfer, meaning it tells us how much energy is transferred every second.

The watt (W) is the unit of power, equivalent to one joule per second (J/s).

Because P = IV and V = IR can be combined: substituting V = IR into P = IV gives P = I²R, allowing power to be found from current and resistance alone.

True.

A higher power rating means more energy is transferred per second, so the device transfers energy more quickly.

Complete the table showing the two equations for electrical power and when to use each.

Using P = IV:

P = 4 × 12

P = 48 W

Work done in a circuit is equal to the energy transferred when charge flows through a component.

The energy transferred depends on the current through the component, the potential difference across it, and the time it is used for.

False.

The time t must always be converted into seconds before substituting into any energy transfer equation.

Energy transferred can be calculated using E = P × t, or equivalently E = I × V × t.

Energy transferred electrically is calculated using E = IVt, where I is current, V is potential difference, and t is time in seconds.

True.

When charge Q flows through a potential difference V, the energy transferred is E = Q × V.

Convert time: t = 60 s

Using E = IVt:

E = 0.7 × 4 × 60

E = 168 J

Complete the table showing each energy transfer equation and what each symbol stands for.

The equations use power in watts (joules per second) and current in amperes (coulombs per second), so time must be in seconds for the units to be consistent.