Electrical Circuits Electric current When river water moves, we say that a current of water flows. And when electric charges move in a wire, we say that an electric current flows. We measure current in Amps (A) Electric current When river water moves, we say that a current of water flows. And when electric charges move in a wire, we say that an electric current flows. We measure current in Amps (A) Voltage the difference in height between the start and end of the river is like the voltage. If the difference is large, the voltage will be large. We measure voltage in Volts (V) Voltage the difference in height between the start and end of the river is like the voltage. If the difference is large, the voltage will be large. We measure voltage in Volts (V) Resistance this can be like the number of obstacles in the river that make it hard to flow. We measure resistance in Ohms (Ω) Resistance this can be like the number of obstacles in the river that make it hard to flow. We measure resistance in Ohms (Ω) charges move round a circuit. They move from one side of a cell or battery, through the wires and components such as lamps, and then into the other side of the battery. charges move round a circuit. They move from one side of a cell or battery, through the wires and components such as lamps, and then into the other side of the battery.

Circuit diagrams We use circuit diagrams so we don’t have to be artists! We draw them with a pencil and ruler. We use circuit diagrams so we don’t have to be artists! We draw them with a pencil and ruler.

Can you name these symbols?

Answers….

Series circuits A television series is one program after another. A series circuit is similar. If you follow the circuit, starting at the cell, it will go through several components but lead straight back to the cell. A television series is one program after another. A series circuit is similar. If you follow the circuit, starting at the cell, it will go through several components but lead straight back to the cell. The problem is, if one component breaks the circuit is broken. eg. cheap xmas tree lights….ask grown ups! The problem is, if one component breaks the circuit is broken. eg. cheap xmas tree lights….ask grown ups! If you put more lamps into a series circuit, the lamps will be dimmer than before.

Parallel circuits In a parallel circuit, if a lamp 'blows' or a component is disconnected from one parallel wire, the components on different wires keep working. Unlike a series circuit, the lamps stay bright if you add more lamps in parallel In a parallel circuit, if a lamp 'blows' or a component is disconnected from one parallel wire, the components on different wires keep working. Unlike a series circuit, the lamps stay bright if you add more lamps in parallel

Measuring current We use an ammeter to measure current The current is the same everywhere in a series circuit. It does not matter where you put the ammeter, it will give you the same reading

The current in a series circuit depends upon the number of cells. The more cells you add, the greater the current The current is not used up by the components in a circuit. This means that the current is the same anywhere in a series circuit, even if it has lots of lamps or other components. The current is not used up by the components in a circuit. This means that the current is the same anywhere in a series circuit, even if it has lots of lamps or other components.

Measuring Voltage Voltage is a measure of the difference in electrical energy between two parts of a circuit. Voltage is a measure of the difference in electrical energy between two parts of a circuit.