LAB: INVESTIGATING SIMPLE CIRCUITS

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PLEASE BE RESPECFUL OF THE MATERIALS. SOME ARE FRAGILE.

USE Ohm's Law: V = RI

V is in volts (V), R in Ohms (Ω) and I in amperes (A)

 

1 mA = 0.001A, 1 mV = 0.001V, 1mΩ=0.001

PURPOSE

 

To study various arrangements of a battery and bulbs and the effect of those arrangements on voltage across the bulbs and the current in the circuit. To verify Ohm’s law. V = R I. To introduce circuit in series and circuit in parallel.

 

 

MATERIALS

 

1 battery and battery holder, bulbs and bulb holders,  wires , 1 multimeter.

 

PROCEDURE

 

secure the bulbs in bulb holder and the battery in the battery holder.

Build a simple circuit : battery  - bulb  - battery      One dash: -  , represent a wire.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3) . Predict the voltage across the battery and the voltage across the bulb:

Vbattery predicted =  __________  and V bulb predicted = _________________

 

4) Using a multimeter, you are going to measure the voltage across the battery and the bulb.

Turn the dial to DCV/20 (direct current voltage with 20V max). One plug in COM and one plug in VΩmA . The picture below shows you how to measure the voltage across the battery.

 

V battery measured = __________ V bulb measured = _________

 

 

Explain any difference with your predictions.

________________________________________________________________

 

_________________________________________________________________

 

_________________________________________________________________
Text Box: V

5) Now measure the current in the circuit. In the multimeter, unplug the VΩmA terminal to 10ADC. Move the dial to 10A section. From now on, remember this procedure to measure the current. Make the circuit battery - bulb - multimeter - battery. See picture.

The current in the circuit is I = ______ A.

This current is large because the resistance of the whole circuit (bulb + wires) is really small. Using Ohm’s law compute the resistance of the whole circuit. (use the voltage across the battery).

 

R = ______ Ω

6) Now place 2 bulbs in series: battery - bulb - bulb - battery

Predict the voltage across each bulb:

 

V1predicted = _______________ V2 predicted = _________

7) Using a voltmeter check your predictions. You need the 2 connections: COM and VΩmA to find the voltage. Remember that from now. Move the dial to DCV20.

 

V1 = _____________ V2 = ________________

 

Where you right ?
Text Box: VText Box: V

8) Measure the current in the circuit. Move one plug again to 10ADC. Battery - bulb - bulb - multimeter - battery

 

I = ___________ A

9) Place the bulbs in parallel. First do the simple circuit battery - bulb - battery. Then connect another bulb across the first one. Are the bulbs brighter when they are connected in parallel compared to when they are connected in series 6)? __________________________

10) Predict the voltage across the bulbs. V1 = ____________ V2 = _______________

11) Use the mutlimeter to check your prediction. 1 plug in COM and 1 plug in VΩmA. See figure.

V1 = _____________ and V2 = ___________________

 

12) The brightness of 2 bulbs connected in parallel are greater then ? Less than ? Same as ? 2 bulbs connected in series.

 

So more brightness means more energy to draw from the battery. Do you expect the current in your parallel circuit to be less or more ? ___________________________

 

13) Check your prediction by measuring the current in the circuit. By now you should know what to do. See figure.

I = ________ A