Procedure: In recording data and explaining observation, a diagram is to be drawn for each step of each experiment. Label each diagram to correspond to a step in the directions. The charge distribution on the electroscope is to be indicated and its net charge ( Q = +, Q = - , or Q = O ) is to be stated below each diagram. Investigation A: The Pith-Ball Electroscope The pith-ball electroscope consists of a light, conducting pith ball suspended from a support by means of an insulating string. 1. A. Ground the pith ball by touching it. B. Rub a rubber rod with wool or fur and bring it near the pith ball. C. Remove the rod. 2. A. Ground the pith ball. B. Rub a glass rod with silk and bring it near the pith ball. C. Remove the rod. 3. A. Ground the pith ball. B. Bring a negatively charged rod near the pith ball. C. Touch the pith ball with the rod. D. Remove the rod.
Procedure: In recording data and explaining observation, a diagram is to be drawn for each step of each experiment. Label each diagram to correspond to a step in the directions. The charge distribution on the electroscope is to be indicated and its net charge ( Q = +, Q = - , or Q = O ) is to be stated below each diagram.
Investigation A: The Pith-Ball Electroscope
The pith-ball electroscope consists of a light, conducting pith ball suspended from a support by means of an insulating string.
1. A. Ground the pith ball by touching it.
B. Rub a rubber rod with wool or fur and bring it near the pith ball.
C. Remove the rod.
2. A. Ground the pith ball.
B. Rub a glass rod with silk and bring it near the pith ball.
C. Remove the rod.
3. A. Ground the pith ball.
B. Bring a negatively charged rod near the pith ball.
C. Touch the pith ball with the rod.
D. Remove the rod.
4. A. Charge the pith ball as in 3, by contact.
B. Touch the pith ball with the rod.
C. Remove the rod.
5. A. Charge the pith ball as in 3.
B. Bring a positively charge rod near the pith ball.
C. Remove the rod.
Investigation B. The Braun Electroscope
The Braun electroscope consists of metal disc at the upper end of a metal rod insulated from the case of the instrument. The rod supports a light metal vane free to rotate about a horizontal axis. When the electroscope is charged the vane swings from its normal vertical position to a near equilibrium position. The angle it makes with the vertical is proportional to the charge of the electroscope.
6. A. Ground the electroscope.
B. Bring a negatively charged rod near the disc of the electroscope.
C. Touch the rod to the disc. This is charging by contact.
D. Remove the rod.
7. A. Ground the electroscope.
B. Bring the negatively charge rod to within 3 cm of the disc of the electroscope.
C. Bring the negatively charged rod as close to the disc as possible without a spark jumping from the rod to the disc.
D. Remove the rod, the electroscope has been charged by induction
Electrostatics continued
1. A. B. C.
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