Question

1a) Without a commutator, an electric motor would A) not move at all B) go too fast and burn out C) not allow current to flow through it D) go back and forth instead of always rotating in the same direction E) stop after at most half a turn 1b.) two current loops are parallel to one another. the force between them is attractive: A) never B) always C) when their currents are in the same direction (e.g., both are clockwise) D) when their currents are in opposite directions (e.g., one is clockwise, one is counter-clockwise) 1c) In the right hand rule for the B field at the center of a loop of current: A) The fingers curve in the direction of the B field, the thumb points in the direction of the current. B) The fingers curve in the direction of the current, the thumb is the direction of the B field. C) The middle finger points towards the center of the loop, the index finger points towards the B field, and the thumb point in the direction of the current. D) The middle finger points towards the B field, the index finger points towards the center of the loop, and the thumb point in the direction of the current. 1d) You are a distance R from the center of a loop of current and from a straight line of current (both have the same current). What can you say about the magnitude of the two B fields? A) The B field from the line is about 2 times stronger than the B field from the loop B) The two B fields are the same magnitude C) The B field from the line is about 3 times stronger than the B field from the loop D) The B field from the loop is about 3 times stronger than the B field from the line E) The B field from the loop is about 2 times stronger than the B field from the line 1e) An electromagnet with an iron core amplifies the magnetic field due to the magnet itself by: A) aligning the magnetic domains in the iron with the field of the electromagnet B) scrambling the magnetic domains in the iron using the electromagnet C) orienting the magnetic domains in the iron perpendicular to the field of the electromagnet 1f) A solenoid has a: A) Strong uniform B field inside, directed radially outwards from the solenoid, small B field outside B) Strong uniform B field outside, directed along the axis of the solenoid, small B field inside C) Strong uniform B field inside, directed along the axis of the solenoid, small B field outside D) Strong uniform B field outside, directed radially outwards from the solenoid, small B field inside 1g)A magnetic dipole experiences no torque in a magnetic field: A) when the magnetic dipole moment is perpendicular to the B field B) when the B field is uniform C) when the magnetic dipole moment points in the direction of the B field

Answer 1