Physics B 2020 Unit 3 Test
ANSWERS
This is the test for Physics B 2020
A proton with charge 1.602 x 10^-19 C moves at a speed of 300 m/s in a magnetic field at an angle of 65 degrees. If the strength of the magnetic field is 19 T, what would be the magnitude of the force the charge experiences?

• 8.28 x 10^-16 N (correct answer, your response)

Where are the magnetic field lines of a permanent magnet the strongest?

• Near both the North and South Poles (correct answer, your response)

Look at the picture of a positive charge moving in a magnetic field. Using the right hand rule, which direction will the force be that the charge experiences? The force will be into the screen, pointing away from you (correct answer, your response)

An alpha particle travelling at 2155 m/s enters a magnetic field of strength 12.2 T. The particle is moving horizontally and the magnetic field is vertical. If an alpha particle contains two protons, each with a charge of 1.602 x 10^-19 C and the particle has a mass of 6.64 x 10^-22 kg, what is the radius of the circular path the particle will travel in?

• 0.366 m (correct answer, your response)

What is the cyclotron frequency of an electron entering a magnetic field of strength 0.0045 T? The charge of an electron is -1.602 x 10^-19 C and the mass of an electron is 9.31 x 10^-31 kg

1.23 x 10^8 Hz (correct answer, your response)

If a charged particle is travelling in a helical shape as it moves through a magnetic field, but then the particle gains the opposite charge, what happens to it's travelling path?

• The path remains helical, but it reverses in direction (correct answer, your response)

A conducting loop is placed in a magnetic field. What must be true for there to be a current induced in the loop?

• The magnetic field must be changing (correct answer, your response)

A rectangular loop of length 15 cm and width 8 cm is placed in a horizontal plane. A magnetic field of strength 5.5 T passes through the plane at 18 degrees above the horizontal. What is the flux through the loop?

NOT SURE ABOUT THIS ONE BUT ITS NOT 0.018 TM^2

A conducting coil with 100 loops is placed in a magnetic field. The radius of each loop is 0.075 m. The magnetic field passes through the coil at an angle of 60 degrees. If the magnetic field increases at a rate of 0.250 T/s, what is the emf produced in the coil after 1 second?

• 0.22 V (correct answer, your response)

A transformer coil has 20 turns on one end and 200 turns on the other end. An emf of 300 V comes into the 20 turn end. How much emf comes out of the 200 turn end of the transformer?

• 3000 V (correct answer, your response)

Describe, in your own words, the Right Hand Rule

Your response: If the thumb, the forefinger, and the middle finger of the right hand are bent at right angles to one another with the thumb pointed in the direction of motion of a conductor relative to a magnetic field.

According to Lenz's Law, the induced emf in any conducting wire will always be in what direction? Hint: How does the induced emf relate to the changing magnetic field?

Your response: The direction of many effects in electromagnetism, such as the direction of voltage induced in an inductor or wire loop by a changing current, or the drag force of eddy currents exerted on moving objects in a magnetic field.

Name at least two circumstances in which a charge will NOT experience a force from a magnetic field. Assume both the charge and field are strong enough to sense each other

Your response: The kinetic energy and speed of a charged particle in a magnetic field remain constant. The magnetic force, acting perpendicular to the velocity of the particle, will cause circular motion.

According to Faraday's Law, given a loop of wire in a magnetic field, what two possible things can change to change the flux through the wire?

Your response: The property of the EMF is such that it produces a current whose magnetic field finds the change which produces it. The magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant.

Briefly describe how an electromagnet works Your response: If a wire carrying an electric current is formed into a series of loops, the magnetic field can be concentrated within the loops.