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Hofstra University
PHYS 2A, HW10 soution
Magnetic induction and Faraday’s law
Home reading: Textbook chapter 31
1. A flat loop of wireconsisting of a single turn of cross-sectional area 8.00 cm2 is perpendicular to a magnetic field that increases uniformly in magnitude from 0.500 T to 2.50 T in 1.00 s. What is the resulting inducedcurrent if the loop has a resistance of 2.00 Ω? What is its direction?

and
2. A strong electromagnet produces a uniform magnetic field of 1.60 T over a cross-sectional area of 0.200 m2. Weplace a coil having 200 turns and a total resistance of 20.0 Ω around the electromagnet. We then smoothly reduce the current in the electromagnet until it reaches zero in 20.0 ms. What is the currentinduced in the coil?

Noting unit conversions from and , the induced voltage is

3. Use Lenz’s law to answer the following questions concerning the direction of induced currents. (a) What isthe direction of the induced current in resistor R in Figure (a) when the bar magnet is moved to the left? (b) What is the direction of the current induced in the resistor R immediately after theswitch S in Figure (b) is closed? (c) What is the direction of the induced current in R when the current I in Figure (c) decreases rapidly to zero?

(a) and decreases; therefore, the induced fieldis (to the right) and the current in the resistor is directed .(b) increases; therefore, the induced field is to the right, and the current in the resistor is directed .(c) into the paper anddecreases; therefore, the induced field is into the paper, and the current in the resistor is directed . | |
4. In the Figure below, the bar magnet is moved toward the loop. Is Va – Vb positive,negative, or zero? Explain.

Look in the direction of ba. The bar magnet creates a field into the page, and the field increases. The loop will create a field out of the page by carrying a...