PHYS 11C Lab 9: Changing Magnetic Fields Worksheet

PHYS 101 General Physics

Task:

Before starting to answer the questions on this worksheet you should:

1. Read the lab manual for this experiment (Experiment 9 - Changing Magnetic Fields). You can find the exact part in the Canvas module for

Lab Note: some mathematical symbols are missing from the file containing the lab manual for the course. Read the document posted for lab 9.

2. Review your lecture notes (or textbook) for the topics of magnetic fields, Biot-Savart law,

Faraday’s law, and Lenz’s law.

3. Watch the theory video (if it helps)

4. Watch the experiment video

5. Read this worksheet and complete as much as you can, then come to class on Wed. 11/10 with your questions.

As usual, don’t answer the questions the instructor asks as she presents, answer the ones here instead.

The entire worksheet, in its original format, should be submitted as a single pdf document through Gradescope by Sunday Nov 14 at 11:59 pm. See the course syllabus if you have questions about how to scan or upload your work.

1. Explain what the magnetic flux is as if you were teaching the concept to another Phys11C student. Include at least one drawing (yours or from the web) and clearly explain it. PHYS 11C Laboratory Lab 9 WorksheetProf. Margoniner Changing Magnetic Fields Go to Faraday’s Electromagnetic Lab Phet simulation

2. Go to the Pickup Coil tab. Play with the simulation for a little a while. Figure out what the controls allow you to see or do. Note that there is a set of controls for the bar magnet, and one for the pickup coil. Answer the questions below.

A. How can you create a voltage (or light the lamp)? Select all that apply. increase the strength of the magnet flip the polarity of the magnet move to bar magnet in an out of the wire loop

B. How can you maximize the voltage output (or the lamp’s brightness)? Select all that apply. move the bar magnet very slowly through the coil(s) move the bar magnet very quickly through the coil(s) increase the wire loop area decrease the wire loop area use more wire loops
use just one wire loop

C. Explain how the answers you selected in parts A and B are reflected on Faraday’s law.

3. Go to the Electromagnet tab. Play with the simulation for a little a while, then answer the questions below.

A. When the battery is connected, a current flows through the wire, and a magnetic field is created. The Biot-Savart law quantifies this phenomenon. Please find the mathematical formula for the Biot-Savart law, and explain each term. PHYS 11C Laboratory Lab #9 WorksheetProf. Margoniner Changing Magnetic Fields

B. What happens to the magnetic field when the battery’s polarity is reversed? (toreverse the polarity, drag the battery control all the way to the left)?

C. Why is it that increasing the number of wire loops increases the intensity of the magnetic field?

D. What happens to the magnetic field when an AC power source is used instead of a battery?

E. What happens when you increase the amplitude of the AC current?

F. What happens when you increase the frequency of the AC current?

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