Electricity Cheat Sheet by Phoebe12

Current = how much charge (coulombs, [packets of electr­ons]) passes through a point in a circuit in an amount of time.

As electrons ‘enter’ a component in the circuit, the same number of electrons ‘leave’ the component

1 Joule (J)/1 Coulomb (Q) =

1 Volt (V)

Converts electrical energy into another form e.g. light globe produces heat and light

Electrons move from negative to positive end of a power source (i.e. repelled and attracted)

Rate of flow of electrons (i.e. number of coulombs of electrons passing a point in a circuit per second)

Energy electrons gain from a power source and lose as they move around an electrical circuit

current in amps =

charge in coulombs

As conductors allow electr­icity to flow through a circuit, and insulators do not, resistance is circuit components slowing down or making it harder for electrical current to flow through a circuit.

A thin wire will have more resistance than a thick wire.

Voltmeters need to withstand stored energy (to measure how much energy is going in and coming out of a component such as a light globe). So, they are stronger than ammeters and resist the current a lot more while an ammeter just wouldn’t be able to handle much at all. Re-read the slide on ammeters if this makes no sense.

To connect an ammeter correctly, you need to break the circuit (stop flow, not smash-­break).

Ammeters have almost no resist­ance, allowing as much current to pass through as possible for an accurate reading without disturbing the current too much.

I = Current in Amperes

t = time in seconds

For mA to A: Simply divide mA by 1000.

For A to mA: Simply multiply A by 1000.

In a parallel circuit, the current splits as it turns at each junction, or corner. It divides and is shared among all compon­ents. The globes should also light up equally.

Current is propor­tional to Voltage –More voltage = more current flowing through.

The equation for finding out the Voltage, Current and Resistance is I = V/R, or V=IR. That is, Voltage equals Current x Resist­ance.

energy = current x voltage x time

E is the energy transf­erred in joules, J

V is the potential differ­ences in volts, V

Charge is current multiplied by time so this equation can also be written as:

E is the energy transf­erred in joules, J

Q is the charge in coulombs, C

Different parts of the circuit (wires, globes, resistors, etc.) have different levels of resist­ance.

Resistance is also useful in things like transistor radios and TV sets.

You attach the voltmeter parallel to the component you are testing and not in series. This means you do not need to break the circuit to measure volts.

Voltmeters have a lot of resist­ance. If you connected it in series, it would probably stop the current from going through which isn’t useful or fun.

Components that are connected one after another on the same loop of the circuit are connected in series. The current that flows through each component connected in series is the same.

Components that are connected on separate loops are connected in parallel. The current is shared between each component connected in parallel. The total amount of current flowing into the junction, or split, is equal to the total current flowing out. The current is described as being conserved.

1. Power supply e.g. a battery

3. Conducting path e.g. connecting wires

The power source (eg: a battery) provides the electrons with the energy that is stored inside the power source.

The power supply and load should match in volts.

The number of volts is equal to how much energy per coulomb (packet of electrons) is taken through the circuit from the power supply to the components for use.

electrons (c)