Current and voltage lab for grade 7 science: practical with sample results (free PDF download)

Quick answer: An ammeter measures electric current in amperes and is connected in series, in the loop. This grade 7 science lab on current and voltage gives the aim, the equipment, the safety points, a step-by-step method, sample results and 8 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.

Do the textbook rules for current and voltage really work? In this lab you measure both quantities in a series circuit and in a parallel circuit, using ammeters in the loop and voltmeters across the parts, and check whether the readings add up. The aim is to learn how to connect meters and to judge how close your results should be.

Level: Grade 7 science (Year 8 · Class 7) · Curriculum: MS-PS2-3

Aim

To measure the current and voltage in a series circuit and a parallel circuit, and to test the rules that link them.

Equipment

Two 1.5 V cells in a holder (3.0 V in total)
Two identical 2.5 V torch bulbs in holders
Two digital multimeters used as ammeters (0 to 1 A range) and one used as a voltmeter
Switch and connecting leads

Safety

Start every current reading on the highest range of the meter. Switch the circuit off before you move a meter. Never connect an ammeter straight across the cells or across a bulb. Leave bulbs to cool before touching them.

Method

Build the series circuit with the switch open. Place an ammeter in the loop before bulb 1. Connect a voltmeter across bulb 1.
Close the switch and record the current and the voltage across bulb 1. Open the switch.
Move the voltmeter across bulb 2 and the ammeter to the loop between the bulbs, then after bulb 2. Record each reading. Measure the voltage across the cells with the voltmeter.
Build the parallel circuit. Place an ammeter in the main wire, one in the branch of bulb 1 and one in the branch of bulb 2. Record all three currents.
Measure the voltage across each bulb and across the cells.

Set-ups for the series and parallel circuits. In both, ammeters are in the circuit paths and voltmeters are across the parts.

Results

Sample measurements from one group:

Circuit	Quantity	Reading
Series	Current before bulb 1	0.19 A
Series	Current between the bulbs	0.19 A
Series	Current after bulb 2	0.18 A
Series	Voltage across bulb 1	1.5 V
Series	Voltage across bulb 2	1.4 V
Series	Voltage across the cells	2.9 V
Parallel	Current in the main wire	0.63 A
Parallel	Current in branch 1	0.32 A
Parallel	Current in branch 2	0.31 A
Parallel	Voltage across bulb 1	2.9 V
Parallel	Voltage across bulb 2	2.9 V
Parallel	Voltage across the cells	2.9 V