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Physics 12 Magnetism and Electromagnetism WS. 1) a) What is the magnetic field 40.0 cm away from a long straight wire carrying a current 2A. [B= μ0 I/ (2 π R)= 1μT] b) At what distance is it 0.1mT? [0.004 m] 2) At one instant the two conductors in a long household extension cord carry equal 2A currents in opposite directions. The two wires are 3.00 mm apart. a) Find the magnetic field 40.0cm away from the middle of the straight cord, in the plane of the two wires. [B = 7.5 X 10–3 T] b) At what distance is the magnetic field one tenth as large? [~ 1.26 m] 3) A cylindrical conductor of radius R = 2.50cm carries a current of I = 2.50A along its length; this current is uniformly distributed throughout the cross section of the conductor. a) Calculate the magnetic field midway along the radius of the wire (that is r = R/2) [B =1 x 10–5 T] b) Find the distance beyond the surface of the conductor at which the magnitude of the magnetic field has the same value as the magnitude of the field at r = R/2. [r = 0.05 m] 4) A superconducting solenoid is meant to generate a magnetic field of 10.0 T. a) If the solenoid winding has 2 000 turns / m, what current is required? [I = 3980A] b) What force per unit length is exerted on the windings by this magnetic field? [F/L= IB = 39800 N/m]