The electric field. Charge distribution on conductors
Answers are for parents and teachers.
1
A 5 nC charge at some point of a field feels a force of 10 µN. What is the field strength (N/C)?
2000
2
Find the field strength 4 cm from an 8 nC point charge in a vacuum.
E = 9·10⁹ · 8·10⁻⁹ : 0.04² = 72 : 1.6·10⁻³ = 4.5·10⁴ N/C.
3
How is the force on a negative charge directed relative to the field strength vector?
Opposite to it, since E is defined for a positive charge.
4
Why is the top of a lightning rod made sharp?
Charge is denser at a sharp tip, so charge from the cloud passes there more easily.
5
How can you check that there is no charge inside a hollow metal ball? Describe the experiment briefly.
Insert an insulated test ball into the sphere, touch it to an electrometer: the pointer does not move.