In teams write down as many lab safety rules as possible!

Today.... Recap knowledge of electrical circuits Set up and trouble shoot electrical circuits Determine circuit rules for current.

Measuring current The unit of measure for current is the amp, which has the symbol A. Current is measured using a device called an ammeter. In a circuit diagram, an ammeter is shown by the symbol When measuring the current through a component, the ammeter is always connected in series (in the same loop) with that component. A

Building circuits Keep your work area clear Lay it out as in the circuit diagram Complete the first "loop" first in order. Add the main components first, eg bulbs and cells.

Experiment 1: Current in series circuit 2 A 1. Set up the circuit as shown above. 2. Measure the current using the ammeter at positions 1 and 2.

Experiment 1: Current in a series circuit 3 A 1 2 1. Add another bulb into the circuit. 2. Now measure the current using the ammeter at positions 1, 2 and 3.

Experiment 1: Current in a series circuit – results 2 A 3 Circuit 1 results: Current at position 1 = A Current at position 2 = A Circuit 2 results: Current at position 1 = A Current at position 2 = A Current at position 3 = A

Experiment 1: Current in a series circuit – summary 2 A 3 Circuit 1 The current at different positions in the circuit, before and after the bulb, was the _______. Current is _____ used up by the components in the circuit. Circuit 2 Increasing the number of components in the circuit ________ the current. The current at all points in a series circuit is the _______. same / same / decreased / not

What is a parallel circuit? A parallel circuit is one which contains a point (a junction) where the current can split (point A) or join (point B). This means that there is more than one path around the circuit. A B

Experiment 2: Measuring current in a parallel circuit 1. Place the ammeter, in turn, at positions 1, 2, 3 and 4. A1 A4 A2 A3 2. Record the ammeter readings in the table. Ammeter Current (A) A1 A2 A3 A4

‘Ideal’ Results 1. Place the ammeter, in turn, at positions 1, 2, 3 and 4. A1 A4 A2 A3 2. Record the ammeter readings in the table. Ammeter Current (A) A1 0.30 A2 0.15 A3 A4

Current in a parallel circuit In a parallel circuit, the current that leaves the cell is the same as the current that returns to the cell. A1 A2 A3 A4 A1 = A4 The current does not get used up by the circuit, just the energy that the electrons are carrying.

Current in a parallel circuit The current splits up at the first junction and then joins together at the second junction. A1 A2 A3 A4 The following is always true for this type of parallel circuit: A1 = (A2 + A3) = A4 If the bulbs are identical then the current will split evenly. If the bulbs are not identical, then the current will not split evenly.

Think.... What do your results tell you about the nature of current?

The cell gives the charges energy which they carry to the bulb. Current Current is the flow of charge. The cell gives the charges energy which they carry to the bulb.

Current in series Compare the circuits below In circuit one the charges only have to give their energy to one bulb but in circuit two, the energy has to be split between three bulbs.

Current in parallel In parallel each charge only passes through one bulb so each bulb gains the full amount of energy from the bulb.

Homework