Review Exam 3 Flashcards
The magnetic dipole moment of a current-carrying loop of wire is in the positive z direction. If a uniform magnetic field is in the positive x direction the magnetic torque on the loop is:
in the positive y direction
Choose the correct statement concerning electric field lines:
field lines are close together where the field is large
A “coulomb” is:
the amount of charge that flows past a point in one second when the current is 1A
The magnetic field B inside a long ideal solenoid is independent of:
the cross-sectional area of the solenoid
When a small voltage is generated across the width of a conductor carrying current in an external magnetic field, the effect is called the ____ effect.
Hall
The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials. The field direction is:
one of the directions of the velocity when the magnetic force is zero
An electric field is most directly related to:
the force acting on a test charge
A bar magnet is moved at a steady speed of 1.0 m/s towards a coil of wire which is connected to a center-zero galvanometer. The magnet is now withdrawn along the same path of 0.5 m/s. The deflection of the galvanometer is in the:
opposite direction as previously, with the magnitude of the deflection halved
An electron is moving north in a region where the magnetic field is south. The magnetic force exerted on the electron is _____.
Zero
Two long straight wires carrying the same current 15 A exert a force of 0.001 N per unit length on each other. What is the distance between the wires?
4.5 cm
The figure below shows a rectangular coil of wire placed in a magnetic field and free to rotate about axis AB. If the current flows into the coil at C, the coil will:
commence to rotate clockwise
Two long straight wires carrying the same current I and separated by a distance r exert a force F on each other. The current is increased to 4I and the separation is reduced to r/6 . What will be the force between two wires? Let Fo = F old.
96Fo
For loop of a current-carrying wire in a uniform magnetic field the potential energy is a minimum if the magnetic dipole moment of the loop is:
in the same direction as the field
The magnetic field outside a long straight current-carrying wire depends on the distance R from the wire axis according to:
1/R
Lines of the magnetic field produced by a long straight wire carrying a current are:
circles that are concentric with the wire
With an electromagnet,
Both more current and more coil turns mean a stronger magnetic field and if there is no current in the coil, there is no magnetic field.
A small 1-mm-diameter circular loop is at the center of a large 20-cm-diameter loop. Both loops lie in the same plane. The current in outer loop changes from 2 A to 10 A in 5 seconds. What is the induced current in the inner loop if its resistance is 1 ohm?
0.4 x 10¯¹¹ A
Two long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the magnetic field they produce is:
non-zero and perpendicular to the plane of the two wires
An electron travels due north through a vacuum in a region of uniform magnetic field that is also directed due north. It will:
be unaffected by the field
If R is the distance from a magnetic dipole, then the magnetic field it produces is proportional to:
1/R³
The figure shows the motion of electrons in a wire that is near the N pole of a magnet. The wire will be pushed:
upwards
A closed magnetic circuit of cast steel contains a 6 cm long path of cross-sectional area 1 cm² and a 2 cm path of cross-sectional area 0.5 cm². A coil of 200 turns is wound around the 6 cm length of the circuit and a current of 0.4 A flows. Determine the flux density in the 2 cm path, if the relative permeability of the cast steel is 750.
1.51 T
An electron moves in the negative x direction, through a uniform magnetic field in the negative y direction. The magnetic force on the electric is in the ______.
negative z direction
A constant current is sent through a helical coil. The coil:
tends to get shorter
The current is from left to right in the conductor shown. The magnetic field is into the page and point S is at a higher potential than point T. The charge carriers are _____.
Positive
