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1) An RC circuit contains a 6 uG capacitor and a 2 ohm resistor. Assuming the ca

ID: 2278311 • 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?                 

Explanation / Answer

time constant T = Rc = 6*106-6 * 2 = 12 us

apply V = vo (1-e^-t/Rc)

1-e^-t/RC = 0.5

e^-t/Rc = 1-0.5 = 0.5

-t/RC = ln ( 0.5) = -0.693

t = 0.693 * 12 = 8.312 us


b. F = qvB sin theta

sin theta = F/qvB

=33.8 *10^-9 /( 1.6*10^-19 * 2.5*10^8 * 2000)

sin theta = 0.4225

theta -= 24.99 deg = 25 deg