Electric current and current sources
Answers are for parents and teachers.
1
Why does current flow when a charged electrometer is connected to the ground, and why is it short?
A field arises between the electrometer and the ground; once its charge has gone to the ground the field vanishes.
2
Draw a diagram of a pocket torch (battery, lamp, switch) and explain the open and closed states.
A series loop: source – switch – lamp. With the switch open the lamp is off, closed it lights.
3
How does energy change in: a torch lamp, a dry cell, an electric stove?
Lamp: electrical → light and heat; dry cell: chemical → electrical; stove: electrical → heat.
4
Why is it dangerous to join the poles of a battery directly with a wire?
With no consumer the current grows sharply and the wire and battery heat up; this is a short circuit.
5
List three current sources at home (e.g. remote batteries, phone accumulator, watch cell) and say which are rechargeable.
A phone accumulator is rechargeable; ordinary remote batteries and watch cells usually are not.