A coil is connected to a sensitive meter with no battery, and a bar magnet is held motionless halfway inside it. What condition decides whether the meter registers current?

A straight wire passes over a compass. The compass needle deflects only during one trial. What condition must have been different in that trial?

A wire segment lies in a uniform magnetic field. Which condition gives the largest magnetic force on the wire?

A student wraps insulated wire around a nail and connects it to a power supply. Which change would most directly make the nail act as a stronger temporary magnet?

A rectangular loop rotates between two magnetic poles. Which condition is required for an emf to be produced in the loop?

Two separate coils are wrapped on the same iron ring. A lamp on one coil flashes only when a switch in the other coil is opened or closed. What condition causes the flash?

A strong magnet falls through a copper pipe and drops more slowly than it does in air. What condition allows this magnetic braking to occur?

A wire loop moves at constant speed into a region of uniform magnetic field, then later moves fully inside it. When is current induced?

A student writes, 'If you cut a bar magnet in half, one half is only a north pole and the other half is only a south pole.' Which correction is right?

A student claims, 'The current induced in a coil flows the same way whether a magnet is pushed in or pulled out.' Which correction is right?

A student says, 'Magnetism is just static electric charge stuck on an object.' Which correction best replaces that idea?

A student predicts that a bar magnet will pick up aluminum foil and copper wire because all metals are attracted to magnets. What should the student conclude instead?

A student says, 'A coil with more battery voltage is always a stronger magnet, no matter the current.' Which correction is best?

A compass is brought near the north pole of a bar magnet. A student says the compass's north end must point toward that pole. Which correction is right?

A student draws magnetic field lines that begin at a north pole and stop at a south pole. What correction should be made?

A student writes, 'Machines that turn motion into current and machines that turn current into motion are unrelated.' Which correction is right?

A student says, 'A loop spinning at a steady rate in a magnetic field makes a current that always flows the same way.' Which correction is best?

A student says, 'Two coils on an iron core can change DC voltage continuously with no moving parts.' Which correction is right?

A student says, 'Current is used up when a coil makes a magnetic field.' Which correction is best?

Use the bar-magnet field-line figure. Where is the magnetic field strongest?

Use the bar-magnet field-line figure. What direction do the outside field arrows show?

Use the two-magnet field-line figure. What does the dense pattern between the facing poles show?

Use the two-magnet field-line figure. What does the pattern in the gap between the facing ends show?

The arrows are hidden in this wire field-line figure. Viewed on the page, which way do the field lines circle the current?

The arrows are hidden in this wire field-line figure. Viewed on the page, which way do the field lines circle the current?

Use the wire field-line figure with points A and B. Which point has the stronger magnetic field?

Use the wire field-line figure with points A and B. Which statement about field strength is supported?

Use the solenoid field-line figure. Where is the field shown as most uniform?

Use the solenoid field-line figure. What does the line spacing show about the field inside compared with outside?

A sealed unit is pressed against a bicycle tire. When the wheel turns, a lamp wired to the unit glows with no battery. What device is inside, and what conversion occurs?

A battery sends current through a coil between magnetic poles, and the shaft attached to the coil starts spinning. What device behavior is being shown?

A plug-in box has two coils wound around the same iron core. It takes 120 V AC from a wall outlet and provides 12 V AC to a lamp, with no moving parts. What is it?

Pressing a switch sends current through a coil, pulling an iron armature so a bell hammer moves. What part is causing the motion?

A steel guitar string vibrates near a coil and magnet, and a matching changing voltage is sent to an amplifier. Which principle explains the signal?

A hand crank on a flashlight is turned, and the bulb lights after a magnet and coil inside are spun. What energy conversion is happening first?

A paper cone moves back and forth when an audio current passes through a coil in a permanent magnetic field. Which interaction drives the cone?

A pointer needle rotates when current passes through a small coil between magnetic poles. Which energy conversion is being used?

A charging pad contains a coil carrying alternating current, and a nearby coil in a phone receives energy through the plastic case. What process transfers the energy?

Water turns a turbine shaft connected to coils and magnets, and the output is delivered as electric power. What device behavior is described?

A door stays locked because current in a coil makes a metal core strongly attract an iron plate. What is the main device inside the lock?

A flat cooktop remains fairly cool, but a steel pan above it heats because changing magnetic fields drive currents in the pan. What explains the heating?

A small fan turns only when its battery sends current through coils near permanent magnets. Which statement best describes the device behavior?

A Hall probe next to a magnet reads 0.080 T. Which quantity is the probe reporting?

A calculation for a loop gives BA cos theta = 0.024 T·$m^2$. Which quantity has been calculated?

A lab sheet asks for the vector B at a point near a magnet. What does B represent?

A coil's magnetic flux changes from 0.10 Wb to 0.30 Wb in 0.20 s. Which quantity most directly controls the size of the induced emf?

In the solenoid relation B = mu0NI/L, what does N/L describe?

A straight wire sits between the poles of a magnet. When a current is switched on in the wire, the wire jumps sideways. What causes the push?

A compass needle is used to mark arrows on a field map around a magnet. Which property is the compass showing at each point?

The unit ${\text{Wb/m}}^2$ is equivalent to which SI unit used for B?