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Name: ____________________________________________________ Date: ______________ Hour: ________
Resistance Lab
Due: 3/23/16
Last day to turn in late: 4/6/16
Aim: Create simple circuits and measure the electromotive force and potential difference at different points in the
circuit.
Pre-Lab Questions:
1. Define ‘electromotive force’
______________________________________________________________
2. Define ‘potential difference’ _____________________________________________________________
3. Define ‘current’_____________________________________________________________
4. Define ‘resistance’_____________________________________________________________
5. When measuring emf and pd, do we connect the multimeter in series or parallel? __________________
6. When measuring current, do we connect the multimeter in series or parallel? __________________
Materials:
 1 D-Cell battery & holder
 1 Unknown Resistor (Mr. Mac will give this to you)
 5 Wires
 1 Switch
 1 Lamp & Holder
 1 Multimeter
Procedure:
1. Just a reminder – you are using electricity to do work, please be careful and responsible with the
equipment.
2. Please create a circuit connecting the following in series (a circle or loop): 1 battery, 1 lamp, and a switch.
3. Draw a picture of your circuit in the space below. Take a look at your notes on how to draw a proper
circuit. (You shouldn’t be drawing a detailed sketch of everything, use the symbols we used in our notes
or make simple, labeled, rectangles.
4. Measure the EMF using the probes of the voltmeter
and record it in the data table. Use the picture to the
right to help you. The multimeter setting should be
on 20V.
5. Measure the potential difference of the lamp and record it in the data table. Use
the picture to the right to help you. The multimeter setting should be on 20V.
6. Add to your sketch from step #3 the multimeter’s position when you measured
the potential difference of the lamp.
7. Measure the current of your circuit and record it in
the data table. For this, spin the dial to “200mA”. It’ll
be in green. This will give you the current in
milliamps. Use the picture to the right to help you.
Remember, your multimeter must be in series when
measuring current. You will now need to add the
fourth wire to connect the multimeter in series.
8. Add to your sketch from step #3 the multimeter’s position when you measured the current.
9. Add an unknown resistor (ask Mr. Mac for it). Add this resistor to
your circuit. You will need to add a 5th wire.
10. Repeat steps 4-8.
Results:
Data Table 1
Emf (V)
PD across the
lamp (V)
Current (mA)
Current (A)
Resistance (Ω)
1 Battery & 1
Lamp
1 Battery, 1
lamp, and 1
resistor
Post Lab Questions:
1. Calculate the resistance of your circuit in the table above. Use the measurement for emf and current.
Make sure when you calculate the resistance, the current has been converted from
this, you divide your mA number by 1,000.
mA to A.
In order to do
2. Using data table 1, determine the resistance of your unknown resistor. ____________________________ You
should probably compare both resistances in the table in order to do this.
3. Explain what happened to your circuit when you added the unknown resistor. Respond in terms of lamp pd,
current, resistance, what your qualitative observations (think about the blub). _____________________________
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4. Was there still current flowing through the circuit after you added the unknown resistor? Explain. ___________
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