Electricity and Magnetism Answers

A point charge q1 = +2.40 µC is held stationary at the origin. A second point charge

q2 = - 4.30 µC moves from the point x = 0.150 m, y = 0 to the point x = 0.250 m, y = 0.250 m.

How much work is done by the electric force on q2.

A small sphere with a mass of of 4.00 X 10-6 kg and carrying a charge of 5.00 X 10-8 C hangs

from a thread near a very large, charged insulating sheet, as shown below. The charge density on

the surface of the sheet is uniform and equal to 2.50 X 10-9 C/m2

. Find the angle of the thread.

A very long uniform line of charge has charge per unit length 4.80 µC/m and lies along the x￾axis. A second long uniform line of charge has charge per unit length – 2.40 µC/m and is parallel

to the -axis at y = 0.400m. What is the net electric field (magnitude and direction) at the following

points on the y-axis: (a) y = 0.200 m and (b) y = 0.600 m?

A 6.20 μC point charge is at the center of a cube with sides of length 0.500 m. (a) What is the

electric flux through one of the six faces of the cube? (b) How would your answer to part (a)

change if the sides were 0.250 m long? Explain

a proton moving horizontally at 3.5x10^4 m/s enters a uniform magnetic field of 0.075 t directed upward at 30°with the horizontal. find the magnitude of the magnetic force acting on the proton

7. Using the formula at the beginning of this lesson, calculate the wavelength of a signal from KPhET 98.7. Remember that FM stations transmit in the Megahertz range. This means that KPhET is transmitting a frequency of 9.87 x107 hz. What is the wavelength of the signal from this radio station?

8. My favorite radio station is NPR, which transmits a signal that is has a wavelength of 3.38 m. What is the frequency of this signal? Remember, light speed is 3 x108 m/s.

9. AM 630 is where I listen to sports. The frequency is 630 khz (or 630,000 hz). What is the wavelength?

10. Pick your favorite radio station, or one your friends listen to. What is its frequency and wavelength?

The force between a 100 kg man and the Earth is 980 N. How close must two protons (1.6 X 10^-19 C) be to generate the same force?

Two electrons are 10^-5 m apart. One electron is fixed on its position. The other, originally at rest, is released. How fast is the free electron moving when it is 10^−3 m from the fixed charge? Apply conservation of energy.

A positive and negative charge, each of magnitude 3.7 * 10 ^ - 6 * C are separated by a distance of 25 cm. Find the force on each of the particles .

Two electrons in an atom are separated by 1.5 * 10 ^ - 10 m , the typical size of an atom. What is the electron forces between them?