Category Archives: Capacitance

R.C. Circuit

Demo: EM-C-RC
Pira Index: 5C 30.30

  1.  Capacitive circuit
  2. Edison cell battery
  3. 2 BA leads
  1.  Connect battery to capacitive circuit.
  2. Charging the capacitor through R1: Sw. S1 position A, Sw. S2 – position A watch the light (R1) and time it. This is the time it took for the capacitor to charge.
  3. To discharge the capacitor to charge. Sw. S1 to position B. Notice the discharge across the light bulb is equal to charge time.
  4. Charging the capacitor through R2: S1 – Position A, S2 – Position B
  5. Repeat steps 2 and 3. Compare the charge and discharge times through R1 and R2.


Leyden Jar (Dissectible)

Demo: EM-C-LJ
Pira Index: 5C 20.30

  1.  Wimshurst machine (or Van de Graaff)
  2. Leyden jar (dissectible)
  3. Discharging tongs
  4. PVC pipe (1/2 inches about 12 inches long)
  5. 2 copper wires
  6. Clear plexiglas box
Note: Leyden jar can be used with Van de Graaff instead of Wimshurst (needs only #1,2,3,4, and 6)
  1.  Set up as shown, 1 copper wire to outer cup of Leyden jar, other wire to handle of the inner cup.
  2. Charge jar by cranking Wimshurst.
  3. Using PVC pipe, carefully remove the inner cup of Leyden jar. Grab glass by the edge and remove from outer cup. Place on plastic box.
  4. Connect the inner metal cup with the outer metal cup using the discharge tongs (no spark).
  5. Using PVC pipe, reassembled jar, connect the inner and outer piecers using discharge tongs (spark).
Caution: to discharge the Wimshurst, carefully swing the discharge arms to the middle of the apparatus until they touch.


Induced Current Storage

Demo: EM-C-IC
Pira Index: 5C 30.00

  1. Capacitor
  2. Iron core coil
  3. 2 B-A leads
  4. 2 B-B leads
  5. Edison cell battery
  1. First connect the BA leads to the coil and one alligator end to the battery. Touch the other alligator end to the opposite end of the battery and observe the spark.
  2. Connect the capacitor into the circuit as shown. Again touch the alligator end to the battery and observe how the capacitor has absorbed the charge, thus reducing the spark.


Film Canister Leyden Jar

Demo: EM-C-FC
Pira Index: 5C 10.00

  1.  Film canister leyden jar
  2. PVC electrophorus with charge plate
  3. Discharging tongs
  4. Paper towel
Before using, fill the canister leyden jar about 3/4 full of water.
Before returning the canister to the shelf be sure it is emptied and dried out.
  1.  Charge up the electrophorus by rubbing the base with the paper towel. Place the plate with the cup handle on the base. Touch the plate with your finger, then lift the plate by the cup.
  2. Touch the plate to the top of the small leyden jar.
  3. Repeat steps 1 and 2 several times.
  4. Touch the top and bottom of the canister with the discharging tongs.



Demo: EM-C-EC
Pira Index: SC 10.20

  1.  Braun electroscope
  2. Pasco slide capacitor on orange base
  3. 10″ x 12″ glass sheet
  4. Zerostat
  5. 2 B-A lead
  1.  Connect the apparatus as shown and place the glass sheet between the capacitor plates.
  2. Hold the zerostat near the electroscope’s center. Slowly pull the trigger to spray charge onto the electroscope. Move the zerostat away before releasing the trigger. The electroscope indicator should rise slightly (you may have to tap the electroscope case).
  3. Pull the glass up and out from between the plates. The indicator should rise as charge leaves the capacitor and flows onto the electroscope. Slide the plates apart (reducing capacitance further) and the indicator will rise higher.
  4. Replace the glass and slide the plates together.


Capacitors Board

Demo: EM-C-CB
Pira Index: 5C 10.10

  1.  Orange capacitors board
  1.  Show and explain.
    A capacitor is a device consisting essentially of two conducting surfaces separated by an insulating material or dielectric such as air, paper, mica, glass, plastic firm, or oil. A capacitor stores electrical energy, blocks the flow of direct current and permits the flow of alternating current to a degree dependent upon the capacitance and the frequency.