November 15, 1993 Midterm Exam 2
No deflection means only that the resultant force is zero; the magnetic force may be balanced by an electric force with crossed E and B fields.
It could be the case that only an E field is in the region.
The induced emf opposes the change in B flux; in the presence of a decreasing field with fixed area, the current will be induced so that the B field it would create would be in the same direction as the inducing field.
1. b. In which direction will the electron circulate?
1. c. What circuit element would convert it into an ammeter that reads 3.0 mA full scale?
3.6 ohm resistor in parallel
|capacitive branch||inductive branch||power supply|
|initial current (mA)||100||0||100|
|final current (mA)||0||500||500|
|time constant (microsec)||100||50||n/a|
|current (mA) after 50 microsec||60||320||380|
3. b. Given a solenoid of length 50 cm, diameter 10 cm, 250 turns, which carries a current of 5.0 A, evaluate the magnetic field.
3. c. If the current drops steadily to zero in 10 ms, what emf is induced in a single-turn loop (diameter 50 cm) outside the solenoid?
4. c. Now estimate the inductance per unit length.