Moving Charges and Magnetism

An electric current is traveling in a wire. A compass is placed under the wire with the current flowing from north to south. In response, the compass needle will-

• rotate because of a magnetic force that acts on the needle

• rotate because of an electric force that acts on the needle

• not move because moving electric charges do not exert magnetic forces on the needle

• not move because moving electric charges do not exert electric forces on the needle

Diagrams of electric fields and magnetic fields often look similar. What is an important difference between electric field lines and magnetic field lines?

• Electric field lines always point away from the object generating the field, while magnetic lines always point toward it.

• Electric field lines are close together where the electric field is strong, but magnetic lines are close where the magnetic field is weak.

• Electric field lines start and end on charges, while magnetic field lines form closed-loop paths to and from the poles.

• Magnetic field lines cannot cross, while electric field lines can

Dave notices that a wire is magnetic and attracts metal objects, What can be concluded about the wire?

• an electric current is passing through it

• heat is passing through it

• radiation is passing through it

• sound waves are passing through it

How are the two forces that make up electromagnetic forces related?

• both are static

• both can be positive, negative, or neutral

• both the electric and magnetic forces are caused by the motion of charged particles such as electrons

• both gravity and light are caused by the motion of charged particles such as electrons

Why does current flowing through a wire create a magnetic field?

• because magnetic force is another aspect of electrical force

• because the metal in the wire attracts magnets

• because magnets can create electricity

• because the draw of a wire can be stronger than the pull of Earth’s magnetic field

An electrical current flows down the power line. What type of force would the flow of the current produce around the power line?

• mechanical

• gravitational

• magnetic

• chemical

How could you make a stronger electromagnet?

• more coils of wire

• add an iron core

• more current in the wire

• all three

What are the microscopic regions of atoms with a commonly aligned magnetic field called?

• micromagnets

• amps

• magnetic zones

• magnetic domains

F = qvB If the speed and charge double, what happens to the magnetic force?

• halves

• remains the same

• doubles

• quadruples

What will happen when these magnets are brought close together?

• They will attract each other.
• They will repel each other.
• Both magnets will turn to the left
• Both magnets will turn to the right