Circuits

Circuits

Current

• An electric current is a flow of charge, and in a wire this will be a flow of electrons. We need two things for an electric current to flow:

• something to transfer energy to the electrons, such as a battery or power pack

• a complete path for the electrons to flow through (an electric circuit)

simple series circuits

The simplest complete circuit is a piece of wire from one end of a battery to the other. An electric current can flow in the wire from one end of the battery to the other, but nothing useful happens. The wire just gets very hot and the battery loses stored internal energy – it ‘goes flat’ and stops working.

measuring current

• A device called an ammeter is used to measure current. Some types of ammeter have a pointer on a dial, but most have a digital display. To measure the current flowing through a component in a circuit, you must connect the ammeter in series with it.

• IN A SERIES CIRCUIT, CURRENT WILL BE THE SAME AT ANY POINT IN THE CIRCUIT

Multiple Choice

Name the components

• Batteries

• Bulbs

• Resistors

• Cells

Multiple Choice

The reading on Ammeter 1 is 2 Amps. What is the reading on Ammeter 2?

• 3 amps

• 2 Amps

• 4 Amps

• 1 Amp

Multiple Choice

The reading on Ammeter 3 is 0.5 Amps. What is the reading on Ammeter 1?

• 4 Amps

• 1 Amp

• 0.5 Amps

• 2 Amps

Multiple Choice

What is this?

• Cell

• Battery of cells

• Bulb

• Ammeter

Multiple Choice

What is this?

• Resistor

• Thermistor

• Fuse

• Variable resistor

Multiple Choice

What is this?

• Battery of cells

• Cell

• Fuse

• Diode

Multiple Choice

Which one is a variable resistor?

Multiple Choice

Which one is a resistor?

Series Circuits cont.....

• All of the components appear one after another THEY ARE IN SERIES

• Current is also measured in series

• Remember: CURRENT IS THE SAME AT ANY POINT IN A SERIES CIRCUIT.

Voltage in series

• Potential difference is measured in volts. The symbol for volts is V.

• For example, 230 V is a bigger potential difference than 12 V. Instead of talking about potential difference, people often talk about voltage, so you may hear or see ‘voltage’ instead of ‘potential difference’.

Measuring potential difference

• Potential difference is measured using a device called a voltmeter. Just like ammeters, some types have a pointer on a dial, but most have a digital display. However, unlike an ammeter, you must connect the voltmeter in parallel to measure the potential difference across a component in a circuit.

• 
  

Voltage is shared between components

Multiple Choice

Voltage is measured in.................. to a component

• series

• parallel

Multiple Choice

Current is measured in .............. to a component

• series

• parallel

Multiple Choice

Voltage is .....................

• the same everywhere

• shared between components

Multiple Choice

current is ...................

• the same everywhere

• shared between components

Multiple Choice

The cell has a voltage of 10 Volts (Voltmeter A). Voltmeter C reads 5 Volts, what is the reading on Voltmeter B?

• 10 Volts

• 5 Volts

• 4 Volts

• 0 Volts

Multiple Choice

Voltmeter B reads 6 Volts. Voltmeter C reads 8 Volts. What is the total Voltage of the Cell (Voltmeter A)

• 12 Volts

• 6 volts

• 8 Volts

• 14 Volts