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APHY101 – Lab #8 – Electrostatics and Circuits
Part A - Electrostatics
Equipment: various rods, paper, balloons, string, wool/felt, silk/rayon, Styrofoam, stopwatch
Procedure:
1. Charge the electroscope by induction according to the figures on the board. Now rub one of
the objects from the table a few times with a material and slowly move the object near the
electroscope. The response of the electroscope will allow you to determine the charge of the
object.
Object
PVC
Material
Charge of Object (+, - , n)
silk
polyethylene
wool
wood
silk
polyethylene
wool
glass
silk
polyethylene
wool
acrylic
silk
polyethylene
wool
Styrofoam silk
polyethylene
wool
nylon
silk
polyethylene
wool
aluminum silk
polyethylene
wool
Did any object(s) not have a charge? Explain.
2. You will now test a variety of objects to determine their conductivity by timing how long it
takes to drain the electroscope of its charge. Charge the electroscope as you did in step 1. Now
touch the electroscope with an uncharged object from the table and measure how long it takes to
drain all the charge. If the electroscope does not respond within 30 seconds, you may assume
that the object has a low conductivity. Complete the time column first then use this data to
complete the remainder of the table using the following criteria:
a) Conductivity – Excellent, Good, Poor
b) Resistance – High, Medium, Low
Object
wood
glass
Styrofoam
nylon
aluminum
balloon
string
paper
your hand
Time (sec)
Conductivity
Resistance
Insulator/Conductor
Do your answers for conductivity and resistance for each object make sense? Explain. Were
there any objects that were a surprise to you?
Part B - Electrical Circuits
Equipment: batteries, three small light bulbs, wires, multimeter
Procedure:
1. Measure the total voltage of the two batteries: Vbatteries =
volts.
2. Measure the resistance of each bulb using the multimeter. Connect the batteries and bulbs in
a series circuit and measure the voltage across each bulb with the multimeter. Use Ohm’s law to
determine the current in each bulb.
Bulbs in
series
#1
#2
Resistance
(ohms)
Voltage
(volts)
Current
(amps)
Do your voltage values verify those expected in a series circuit? Explain.
3. Repeat steps 1 and 2 using three bulbs.
Bulbs in
series
#1
#2
#3
Resistance
(ohms)
Voltage
(volts)
Current
(amps)
Do your current values verify those expected in a series circuit? Explain.
Measure the resistances of the three bulbs while the bulbs are connected to the batteries. Explain
these new resistance values.
4. Repeat the procedure above with the bulbs in parallel.
Bulbs in
parallel
#1
#2
Resistance
(ohms)
Voltage
(volts)
Current
(amps)
Bulbs in
parallel
#1
#2
#3
Resistance
(ohms)
Voltage
(volts)
Current
(amps)
Comment on the brightness of the bulbs when connected in parallel compared to in series.
Do your current values verify those expected in a parallel circuit? Explain.