A long, straight wire carries a 25.0-A current. An electron is fired parallel to

Question

A long, straight wire carries a 25.0-A current. An electron is fired parallel to this wire with a velocity of 280km/s in the same direction asthe current, 2.00cm from the wire.

a) Find the magnitude of the electron's initial acceleration.

b) Find the direction of the electron's initial acceleration.(Towards the wire, away from the wire, out of the page, or into thepage)

c) What should be the magnitude of a uniform electric fieldthat will allow the electron to continue to travel parallel to the wire?

d) What should be the direction of this electric field?(Towards the wire, away from the wire, out of the page, or into thepage)

e) Is it necessary to include the effects of gravity?

Explanation / Answer

a) B = mue*I/(2*pi*r) = 4*pi*10^-7*25/(2*pi*0.02) = 2.5*10^-4 T

F = q*v*B
m*a = q*v*B

a = q*v*B/m = 1.6*10^-19*2.8*10^5*2.5*10^-4/9.1*10^-31 = 1.23*10^13 m/s^2

b) away from the wire

c)q*v*B= q*E

E = v*B = 2.8*10^5*2.5*10^-4 = 70 N/c

d) towards the wire

e) no. gavitational force is very less comared to electromagnetic firce on electron.

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