Electricity

Direct current

Cells and batteries supply electric current which always flows in the same direction

Alternating current

Constantly changing direction

Conductor

Allows current to flow / pass through

Insulator

Stops current from flowing

Fuse

When the current becomes too high, the fuse will melt and break the circuit

Formula involving current, time, and charge

Q = I x T

Charge © = current (A) x time (t)

Current

Rate of flow of charge

Equation linking voltage, current, and resistance

V = I x R

Voltage (v) = current (A) x resistance (Ω)

If you increase the voltage …

Then more current will flow

If you increase the resistance …

Then less current will flow (more voltage is needed to keep the same current flowing)

Series circuit

In a series circuit, current is the same everywhere; voltage is distributed over the components (doesn’t have to be equal amounts)

Switch

Opens or closes circuit

Voltmeter

Measures potential difference (volts) (must be parallel / over)

Variable resistor

Changes resistance

Battery

Power source

Ammeter

Measures current (must be placed in series)

Parallel circuit

Voltage in each branch is equal to the voltage over the battery

Resistance

Resistance is a measure of how hard it is for the electrons to move in an electrical circuit

What causes resistance?

1.) As the electrons move along the wire they collide with the metal ions in the wire

2.) These collisions make the atoms vibrate more, which makes the metal hotter

3.) All wires and components have some resistance, so electrical appliances always waste some energy as heat

Special resistors (don’t obey ohm’s law)

-Thermistors

-Light-dependent resistors (LDR)

-Diode

-Filament bulbs

Thermistor

The resistance of a thermistor decreases as the temperature increases

Light-dependent resistor (LDR)

The resistance of a light-dependent resistor decreases as light intensity increases

Diode

A diode only allows current to flow in one direction through it. No current is allowed to flow the other way in a diode.

Static electricity

Charges which are not free to move. This causes them to build up in one place and it often ends with a spark or a shock when they do move.

Like charges…

Repel

Unlike charges…

Attract