Source is the device that stores energy and provides the e.m.f. required for the circuit to function.

Switch when closed will allow electricity to flow through the entire circuit. When opened it will break the circuit.

Resistor is a device that limits or resists the current flow. A resistor will increase resistance of the current. It can be fixed or variable.

Lamp will light up when electricity flows through the circuit.

Ammeter measures the amount of current flowing in a circuit.

Voltmeter measures the amount of p.d. across a device in a circuit.

Fuse is a length of wire that melts when a high current flows through it, breaking the circuit and helping prevent any electrical damage or injury.

Current in a circuit is same anywhere in a series circuit which is why you can connect an ammeter anywhere in the circuit and you'll get the same value in amps.

The total resistance in a series circuit is the sum of the resistance of all the resistors in the circuit.

The total p.d. in a series circuit will be the sum of the p.d. across each component in the circuit.

The total p.d. in a series circuit will be the sum of the p.d. across each component in the circuit.

Voltmeters have to be connected parallel to the components it is measuring, since each has a different voltage/p.d.

In a parallel circuit, since the current flowing from the source/battery is larger than the current in each branch (i.e. each straight wire).

The current from the source of a parallel circuit is the sum of the separate branches in the circuit. The current breaks up and take the easiest path first, with some flowing along each parallel branch and re-combining when the branches meet again.

Conventional current flows from the positive end (long line) to the negative end (short line).

The combined resistance of the resistors in a parallel circuit is less than that of the individual resistors.

You can find Total Resistance in a parallel circuit with the following formula: 1/Rt = 1/R1 + 1/R2 + 1/R3 + ......

The voltage across each bulb will be the same, so every bulb will be equally bright.

Each component is independent of other. In a series circuit, if one component breaks down, the entire circuit will be affected. But in a parallel circuit, there are multiple paths for the current to flow.

Each component can be independently controlled by a switch. In a series circuit, one switch controls every component. In a parallel circuit, you can connect switches parallel for component in different branches, to turn them off or on.

Used as temperature sensors, for example, in fire alarms. In the most common type of thermistor, the resistance decreases as the temperature increases.

At low temperatures, the resistance of a thermistor is high and little current can flow through them.

At high temperatures, the resistance of a thermistor is low and more current can flow through them.

Used to detect light levels, for example, in automatic security lights. Their resistance decreases as the light intensity increases.

In the dark and at low light levels, the resistance of an LDR is high and little current can flow through it.

In bright light, the resistance of an LDR is low and more current can flow through it.

A thermistor is a temperature dependent resistor which means that its resistance varies with the temperature of the surrounding. It's resistance reduces when more heat is applied and vice versa. It is used in fire alarms, where a high temperature, indicating a fire, causes the resistance to reduce and more current to flow, activating the alarm. In an automatic air conditioning system, when the room is warm, the resistance drops to activate the cooling.

An LDR or a light dependent resistor, where the resistance decreases when light intensity increase. It's used in burglar alarms, where if a light is turned on, the resistance of the LDR drops and current flows to activate an alarm. It is also used by photographers for automatic shutter control based on the lighting of the surrounding.

Both thermistors and LDRs are called transducers since they convert energy from and form to another. Thermistors convert heat energy into sound energy (in the fire alarm example) and LDRs convert light energy into sound energy (in the case of the burglar alarm)

Power is a measure of how quickly energy is transferred. The unit of power is the watt, W. The more energy that is transferred in a certain time, the greater the power of the appliance. It is calculated using the formula:

power = current x voltage

p = I x v

This can be rearranged to find the current and voltage if the other two values are given:

I = p/v

v = p/i

In an earlier unit, we learned that power = energy/time. Rearranging it with energy as the subject, we get energy = power x time. We know that power = current x voltage. So energy can be written as

energy = current x voltage x time

e = I x v x t

In a circuit, insulation is the plastic sheath that covers wires. If you have damaged insulation, it means that metal wires inside the cable are exposed.

If a person touches the exposed wires, they could be electrically shocked, which may lead to death.

When a very high current is run through a cable, there is a risk of overheating the wire due to too much energy. This overheating could lead to electrical fires.

Since water is a conductor, during damp situations such as inside a bathroom, electricity from the electrical appliance may electrocute nearby people through the conductive water. Even skin, if wet will electrocute the person if they touch a socket.

A fuse protects a circuit

Fuses protect components in a circuit from overheating by breaking circuit. A high level of current flowing through the circuit causes the wires inside the circuit to heat up. The fuse, a metal wire with a low melting point will melt and cause the circuit to break.