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Electricity Lab (Virtual)
Part 1. To investigate Ohm's Law V= I R
V-battery Voltage in Volts,
R-electrical Resistance in Ohms,
I-electrical current in amps
V=IR
and R.
divide both sides of this equation by R to get a new equation for I in terms of V
Write New Equation here:
I=V/R
Click on the button at right to open ohm's law simulator.
1. What happens to I when V increases? ____it increases___________
What happens to I when V decreases?___it decreases____________
What happens to I as V doubles?_____I doubles__________
What happens to I as V halves?_____I halves___________
What happens to I as V triples?_____I triples___________
What happens to I as V drops to one-third?_____decreases 1/3___________
2. What happens to I when R increases? ___decreases____________
What happens to I when R decreases?_____increases__________
What happens to I as R doubles?_______halves_________
What happens to I as R halves?______doubles__________
What happens to I as R triples?_____drops to one-third___________
What happens to I as R drops to one-third?_____triples___________
3. For a battery voltage of 6.0 V what current will you get with a 100 Ohm resistor? (mA means
milliamp……..1000 mA = 1 A)
I= ____60 mA or 0.06Amps______________
4. For a battery voltage of 6.0 V what resistor is needed to limit the current to 10 mA (0.010 A)
?
R= ___600 ohms_____________
5. What battery voltage is needed to cause 30 mA (0.030A) to flow through a 100 Ohm resitor?
V=______3_V_________________
Part 2. To investigate Electrical Resistance R of a wire.
R: Resistance in Ohms
: resistivity of the wire's material in Ohms-cm (Glass is
large copper is small)
L: wire length
A: cross sectional area of the wire.
Click on the button at right to open Resistance simulator.
In your own words explain how the resistance of a wire changes with , L, and A.
Increase in L equals increase in R. Increase in  equals increase in R. Increase in A is decrease in
R.
Two Tungsten light bulb filaments of identical lengths are connected to a household circuit of
120 V. Filament A is thicker than Filament B.
Which filament has the largest electrical resistance? A or
B
circle your answer
When connect to 120 V, which filament has the largest electrical current? A or B
Which filament will glow brightest in your home?
A or B
If one is rated 40 Watts and the other 100 Watts, which one is the 40 Watt bulb? A or B
Part 3. Building simple circuits.
Series
Check the non-contact ammeter check box and move it over different wires in the circuit. How
does the current in the wires compare to the current into (or out of) the battery?
____________________________________________________________________________
Battery Voltage
1 Bulb
50 V
Relative
Current into the Battery Bulb
Brightness
5.0 Amps
bright
2 Bulbs in series
50 V
2.5 Amps
Not so
bright
3 Bulbs in series
50 V
1.67 Amps
Dim
Does the overall current increase or decrease as more light bulbs are added in series?
Decreases
Does the overall effective circuit resistance increase or decrease as more light bulbs are added
in series?
Increase
Check the non-contact ammeter check box and move it over different wires in the circuit. How
does the current in the wires compare to the current into (or out of) the battery?
The current is the same everywhere.
__________________________________________________________________________
Move the voltmeter leads to measure the voltage across each light bulb (see example at right). What is
the relationship between the voltages of each bulb and the total battery voltage?
_1-bulb has the same voltage as battery voltage, 2-identical bulbs each bulb has a voltage equal
to half the battery voltage, 3 -identical bulbs each bulb has a voltage equal to 1/3rd the battery
voltage________
Parallel Circuits.
The first row in this table should be the same as the first row in the table for series circuits.
Battery Voltage
Relative
Current into the Battery Bulb
Brightness
50 V
5.00 amps
Very bright
2 Bulbs in parallel 50 V
10.0amps
Very
bright
3 Bulbs in parallel 50 V
15.0 amps
Very
bright Fire
1 Bulb
Does the overall current increase or decrease as more light bulbs are added in parallel?
increase
Does the overall effective circuit resistance increase or decrease as more light bulbs are added
in parallel?
decrease
Check the non-contact ammeter check box and move it over different wires in the circuit. How
does the current in the wires compare to the total current into (or out of) the battery for parallel
circuits?
_15 Amp leaves battery and 5 Amp go through each individual resistor.
____________________________
Move the voltmeter leads to measure the voltage across each light bulb. What is the relationship
between the voltages of each bulb and the total battery voltage for parallel circuits?
_Each has 50V . That is each has the full battery voltage driving current through it.
Answers for questions below 1. C 2. C 3. A
4. C
5. A
6.A
7. E
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