1) An RC circuit contains a 6 uG capacitor and a 2 ohm resistor. Assuming the ca
ID: 2278273 • Letter: 1
Question
1) An RC circuit contains a 6 uG capacitor and a 2 ohm resistor. Assuming the capacitor is fully charged and discharge begins at
t = 0, at what time is the potential across the capacitor reduced by a factor of one half?
2) A proton is moving through a magnetic field of strength 2 kT with a speed of 2.5*10^8 m/s. If the magnitude of the force of the proton experiences is 33.8 nN, what is the angle between the proton's velocity and the direction of the field?
3) Microwaves in a microwave oven are produced by electrons circling in a magnetic field at a frequency of 2.4 GHz (f = 2.4*10^9 1/s)
a) what is the magnetic field strength?
b) if the electron can orbit with a maximum diameter of 2.5 mm, what is the maximum electron kinetic energy?
4) A 3 m long wire of mass 200 g is suspended in a magnetic field of 0.3 T.
a) if the field points into the page and the wire runs along the x axis, what direction must the current flow for the suspension to occur?
b) what is the magnitude of the current flowing through the wire?
PLEASE SHOW ALL WORK AND EXPLAIN AND I WILL ADD MORE POINTS
Explanation / Answer
1)
time constant, T = R*C = 2*6 = 12*10^-6 s
let at time t V = Vo/2
V = Vo*e^(-t/T)
vo/2 = vo*e^(-t/T)
e^(t/T) = 2
t = T*ln(2)
= 8.318*10^-12 s
2) F = q*V*B*sin(theta)
theta = sin^-1(F/q*v*B)
= sin^-1(33.8*10^-9/(1.6*10^-19*2.5*10^8*2*10^3)
= 25 degrees
3)
f = B*q/(2*pi*m)
B = 2*pi*f*m/q
= 2*3.14*2.4*10^9*9.1*10^-31/1.6*10^-19
= 0.08572 T
4)
a) towards right
b) in the equilibrium
magnetic force = gravitational force
B*i*L = m*g
i = m*g/(B*l)
= 0.2*9.8/(0.3*3)
= 2.178 A
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