Chapter 22
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3). a). Usr the Right Hand's Rule: B filed points down, velocity vector points
forward --> the force on the charges (direction of charge movement)
is directed from the passenger's side to the driver's side of the car.
(For right hand driving cars) Thus the driver's side will
have more positive charge.
b). The induced EMF is
EMF = v * B * L =>
L = EMF/v*B = 0.0024V / 25m/s*0.000048T = 2m
The length of the car is L= 2 meters.
12). Flux through the surface is equal to the surface area A, multiplied by
the normal component of the magnetic field.
PHI = A * B * cos(25degrees)
Surface area is A = pi * r^2, where pi = 3.145...
The flux is
PHI = pi*r^2*B*cos(25 degrees) = 3.14*(0.1m)^2*0.078T*cos25 =
= 2.2*10^(-3) T*m^2
30). The magnetic field induced by the current in the wire is curling around
the wire. In the area of the circuit, it is directed into the page.
As the current increases the flux through the circuit also
increases. The current induced in the circuit will have a direction such
that the magnetic flux generated by the induced current will oppose the
increse of flux due to current in the wire. It means that the flux from
the circuit has to point out of the page and the current that can generate
the field pointing out of the page is flowing in the counterclockwise
direction. Thus, the direction of current through the resistor
is counterclockwise (from the right to the left).
52). Energy stored in the inductor is (formula 22.10)
E = L * I^2/2 = 0.085 H * (2.5 A)^2/2 = 0.26 J
60). The transformer equation (formula 22.12)
V_1 N_1
------- = ---- =>
V_2 N_2
N_2 = N_1 * V_2/V_1 = 21 * (4320 V/120 V) = 756
The secondary coil has N_2 = 756 turns.