Measuring Current in Electrical Circuits a Lab Exercise

Measuring Current in Electrical Circuits – A Lab Exercise Grade 9 Science Name: ______

Obtain the electrical circuit kits and 1 ammeter then follow these steps carefully while answering related questions (*) as you proceed.

Step 1 Notice that some ammeters have different ranges of measurement: Convert the following:

100 mA = A 0.05 A = mA

25 mA = A 0.300 A = mA

A: Series Circuits

Step 2 Connect a circuit as shown in the diagram. Use 2 cells, 1 lamp and 1 ammeter.

*Measure the amount of current at the positions shown. A1 =

*How does the current compare between the above 2 positions? Can you suggest a reason for this result?

Step 3 Connect a circuit as shown in the diagram. Use 2 cells, 2 lamps in series and 1 ammeter.

*How does the current compare at the above 3 positions?

*How do the current readings in step 3 compare to that in step 2? Suggest a reason for the difference.

*Suggest a rule or “law” regarding current in series circuits: B: Parallel Circuits

Step 4 Connect a circuit as shown in the diagram. Use 2 cells, 2 lamps in parallel and 1 ammeter.

A4 = *How does A1 compare to A4? ______

*How does A2 compare to A3? ______

*How does A1 compare to A2 and A3? ______

*Suggest a rule or “law” regarding current in the above circuit:

Step 5 Connect a circuit as shown in the diagram. Use 2 cells, 3 lamps in parallel and 1 ammeter.

*How does A1 compare to A5? ______

*How does A2, A3 and A4 compare to each other? ______

*How does A1 compare to A2, A3 and A4? ______

*Suggest a rule or “law” regarding current in parallel circuits:

The above “laws” are called “Kirchoff’s Current Laws”. Complete the following phrases:

When electric loads are connected in series, the current measurements ______.

When electric loads are connected in parallel, the current measurements ______.

When finished, carefully put the equipment back in the kit containers. Measuring Voltage in Electrical Circuits – A Lab Exercise

Grade 9 Science Name: ______

Obtain the electrical circuit kits and 1 voltmeter then follow these steps carefully while answering related questions (*) as you proceed.

A: Parallel Circuits

Step 1 Connect a circuit as shown in the diagram. Use 2 cells, 1 lamp and 1 voltmeter.

*Measure the voltage at the positions shown. V1 =

*How does the voltage compare between the above 2 positions? Can you suggest a reason for this result?

Step 2 Connect a circuit as shown in the diagram. Use 2 cells, 2 lamps in parallel and 1 voltmeter.

*How does the voltage compare at the above 3 positions?

*How do the voltage readings at the lamps in step 2 compare to that in step 1?

*Suggest a rule or “law” regarding voltage in parallel circuits: B: Series Circuits

Step 3 Connect a circuit as shown in the diagram. Use 2 cells, 2 lamps in series and 1 voltmeter.

*How does V2 compare to V3?

*How does V1 compare to V2 and V3?

*Suggest a rule or “law” regarding voltage in the above circuit:

Step 4 Connect a circuit as shown in the diagram. Use 2 cells, 3 lamps in series and 1 voltmeter.

*How does V2 compare to V3 and V4? ______

*How does V1 compare to V2, V3, and V4?

______

*Suggest a rule or “law” regarding voltage in the above circuit:

The above “laws” are called “Kirchoff’s Voltage Laws”. Complete the following phrases:

When electric loads are connected in series, the voltage measurements ______.

When electric loads are connected in parallel, the voltage measurements ______.

When finished, carefully put the equipment back in the kit containers.