Question

Problem 5: A 5 cm long wire is in a uniform magnetic field of 4T, so that current in the wire is perpendicular to the magnetic field. The wire is connected to a 10 ohm resistor in series, so that the resistance of the wire is negligible. The wire and resister are then connected in series to a charged 1500mF capacitor at 50 kV. A: What is the current through the wire as function of time, with t-0 being when it is connected to the capacitor? 8: What is the force on the wire as a function of time? C: What is the total impulse on the wire for the first 45 seconds? Problem 6: A long thin solenoid 7 mm in diameter and 4 cm long with an inductance of 8 mH and internal resistance of 6 ohms is put in series with a 1.5 V battery. The battery is cylindrical and is taped up against the side of the solenoid so that positive terminal of the battery is next to the part of the solenoid it is connected to, and the same for the negative terminal. an A: If the coil is wrapped in a right-handed fashion going from the positive terminal to the negative terminal, what is the magnetic field inside the solenoid, and is it pointed towards or away from the negative terminal of the battery? 8: If the battery and coil were allowed to float in water like a compass in the city of Redmond, which terminal of the battery would point towards the north pole of the Earth? Problem 1: A ring of conducting wire with a radius of 1.5m and cross-sectional area magnetic field that is uniform in space. The magnetic field is oriented at an angle that is 30 degrees off from normal to the ring's area vector and increasing at a rate of 0.1T/hr. If the resistivity of the wire is 1.7x10 ohm-meters, what is the current density in the wire using Faraday's law and Ohm's Law? of 4 mm2 is placed in Problem 2: An ind uctor of 2mH is put in series with a 50 kn resistor and a 20V DC power supply. A: If the current in the circuit is 0 at t=0, what is the current as a function of time? B: If the inductor is a long thin solenoid that is 5 cm long with a cross section of 2 cm2, what is the magnetic field in the solenoid as a function of time? Problem 3: Two parallel wires carry cu 30A, The wires are separated by 5 cm and are 10m long. rrent in opposite directions, the first at 10A and the second at A: What is the force on each wire? Are the forces acting to push the wires closer or farther apart? B: Sketch the total magnetic field between the wires and outside of the wires.

Answer 1

5] a) current I = V/R * e^(-t/RC)

I = 50e3/10* e^(-t/10*1.5)

I = 5000*e^(-t/15) A

b] Force F = ILB

= 5000*e^(-t/15)*0.05*4

= 1000*e^(-t/15) N

C] Impulse = integral Fdt

= integral 1000*e^(-t/15) from t=0 to t =45

= 14253 Ns