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Moving Charges And Magnetism

Question
CBSEENPH12037671

A solenoid of length 75 cm, has a radius of 1 cm and has a total of 750 turns wound on it. It carries a current of 4A. Calculate the magnitude of the axial magnetic field inside the solenoid. If a proton were to move with a speed of 103 ms–1 along the axis of this current carrying solenoid, what would be the force experienced by this proton?

Solution

Given, a solenoid.
Length of the solenoid, l = 75 cm 
Radius of the coil, r = 1 cm 
Number of turns in the coil, N = 750 
Current carried by the wire, I = 4 A 

Magnetic field inside a solenoid, B = μo n I  

Number of turns per metre = 7500.75 =  1000 turns/m 

Therefore, 
Magnetic field, B = 4π × 10-7 × 1000 × 4 4π×10-7× 1000 × 4 
                       = 16 × 3.14 × 10-4 
                       = 5.024 × 10-3 

Force experienced by the proton, F
                  F = qvB sin θ 
Speed of the proton, v = 103 m/s 
Charge on proton, q = +e = 1.6 × 10-19  C

The direction of magnetic field is along the axis. 
θ is the angle between velocity and magnetic field which is 0in this case .

 sin 0 = 0  
Hence the force acting on proton = 0.