1. Consider a set of conducting metal tracks (two parallel beams with a flat top

Question

1. Consider a set of conducting metal tracks (two parallel beams with a flat top surface) 0.3 m apart. Across the tracks, perpendicular to them, is a conducting rod of mass 0.65 kg. There is a uniform magnetic field of 0.80 T [Tesla, the SI unit of magnetic field strength, 1T = 1 N / (A m),] pointing down. A circuit consisting of a 47w resistor and a 15 V power supply is placed across the rails. What is the acceleration of the rod? Hint: calculate the current, then then force on the rod, and then the acceleration.

2. If the field is pointing downward, and the positive current flows from the bottom rail through the rod into the top rail, will the rod accelerate to the left or the right?

3. A solenoid (coil) has a radius of 7.2 cm, a length of 31.5 cm, and has 380 turns of wire. A current of 350 mA runs through the coil. Calculate the field strength inside the coil.

Explanation / Answer

apply gravitatioanl force = magnetic force

ma = iLB

here i is obtined from ohms law V = iR

so i = 15/47 = 0.3191 Amps

so a   = 0.3191* 0.3 * 0.8/0.65

a = 0.117 m/s^2

2. to the left

]3. B due to solonoid is = u0ni/L

B = 4pi*10^-7 * 380* 0.35/(0.315)

B = 5.303*10^-4 T

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