A flow of electrons - Moves from positive end of cell to negative end - Measured in Amps (A)

It measures the current in a circuit in Amps.

Current is never used in a circuit. In a series circuit, the current is the same all the way round.

What happens to current in a series circuit?

Drawn in the opposite direction. Positive to negative or anticlockwise. Known as conventional current.

Which direction does current flow in circuit diagrams?

The current in the branches add up to the total current leaving the cell.

What is the rule behind current in parallel circuits?

A potential difference of 1 volt tells us that 1 joule of energy is transferred for each coulomb of charge that is moving through the circuit. Measured by voltmeter in volts.

For components connected in parallel, the p.d across each component is the same.

What is the rule behind potential difference in a parallel circuit?

the p.d from one cell multiplied by no. of cells in the battery.

The p.d of the cells cancel out. Positive (larger side) of cell must face left (anticlockwise)

What happens when cells in a battery are facing the wrong direction?

The size of the electric current is the rate of flow of electrical charge. Measure in coulombs. Current of 1 amp = 1 coulomb of charge flowing per second.

What is electrical charge measured in and what’s it equal to? 

Q = I x t - Charge Flow(C) = Current(A) x time(s)

E = Q x V - E.T(J) = Charge Flow(C) x P.D(V)

What is the equation for energy transferred in a circuit?

As electrons move through a component they collide with atoms in the metal. Electrical energy is transferred into other forms e.g. thermal. | The resistance tells us the p.d required to drive a current through a component.

What caused resistance and what does it tell us?

R = V / I - Resistance(ohms) = P.D(V) / Current(A)

Current through a resistor is directly proportional to the potential difference. Graphbis one straight diagonally through the origin.

What is the relationship between current through a resistor and p.d?

1. Resistance is always constant. The resistance does not change if we increase the current. 2. This type of resistor is an ohmic conductor. 3. The resistance will only stay constant if the temp. is constant.

What are some rules regarding resistors and they’re relationship with current?

1. Current through filament lamp is not directly proportional to p.d. 2. Theinsi because filament lamp gets hot, leading to increase in resistance. 3. At high temps, atoms in filament vibrate and so the electrons in the current now collide more with the atoms. Therefore more energy is needed to push current through filament.

Explain the formation of a filament lamp graph.

Diodes have a very high resistance in the reverse direction -> one directional current. graph starts rising off the middle of halfway x-axis.

1. With two resistors in parallel, we have two pathways for the current to take, more total current will flow through the circuit. 2. If the current has increased but the p.d has not changed, then the total resistance must have decreased.

When resistors are in parallel, why is the total resistance less than the smallest individual resistor value?

The resistance of a thermistor decreases if the temperature increases?

Power is the rate at which energy is transferred. Power(W) = P.D(V) x Current(A)

Power(W) = Current(A) SQUARED x Resistance (Ohms)

If we know the current through a component and the resistance of a component, what equation would we use for power?

What is the frequency and p.d of the UK Mains Supply?

The live wire -> carries the alternating P.D (230V) from supply. Live wires is connected to fuse in the plug.

What is the name of the brown wire in a 3-core cable and what is its role?

The neutral wire -> Completes the circuit. P.D = 0V compared to live wire.

What is the name of the blue wire in a 3-core cable and what is its role?

The earth wire -> acts as a safety wire to stop appliance becoming live.

What is the name of the green/yellow wire in a 3-core cable and what is its role?

1. Step-up transformers increase the P.D to several hundred thousand volts. 2. Less energy is lost in the power cables when the P.D is very high. 3. The electricity passes through high-voltage cables. 4. The electricity passes through step-down transformers which reduces P.D to 230V. 5. Electricity then passes to homes. KF: NG is system of transformers and cables.

AQA Triple Physics Paper 1 Electricity

Flashcards

Electricity - series and parallel circuits

science revision

AQA Triple Physics Paper 1 Electricity

Flashcards

Electricity - series and parallel circuits

science revision