# High School Physics : Electricity and Magnetism

## Example Questions

### Example Question #3 : Magnetism And Electromagnetism

A current runs through a straight wire from right to left. What direction would the magnetic field be?

Into the screen

Left to right

Counter-clockwise

Right to left

Out of the screen

Counter-clockwise

Explanation:

For this problem, use the right hand rule. Take your right hand, stick your thumb straight up and curl your fingers around in a "thumbs up" shape.

If your thumb is the current, your fingers will be the magnetic field. With your thumb pointing to the left (the direction of the current), your fingers will curl in a counter-clockwise direction.

Note that the right hand rule for a straight wire is different from the right hand rule for a planar magnetic field!

### Example Question #4 : Magnetism And Electromagnetism

A straight wire carries a current directly into your computer screen. In what direction would the magnetic field be?

Counter-clockwise

Into the screen

Out of the screen

Right to left

Clockwise

Clockwise

Explanation:

For this problem, use the right hand rule. Take your right hand, stick your thumb straight up, and curl your fingers around in a "thumbs up" shape.

If your thumb is the current, your fingers will be the magnetic field. With your thumb pointing away from your face, or toward your computer screen (the direction of the current), your fingers will curl in a clockwise direction.

Note that the right hand rule for a straight wire is different from the right hand rule for a planar magnetic field!

### Example Question #5 : Magnetism And Electromagnetism

A straight wire carries a current directly out of your computer screen. In what direction would the magnetic field be?

Out of the screen

Left to right

Into the screen

Counter-clockwise

Clockwise

Counter-clockwise

Explanation:

For this problem, use the right hand rule. Take your right hand, stick your thumb straight up, and curl your fingers around in a "thumbs up" shape.

If your thumb is the current, your fingers will be the magnetic field. With your thumb pointing toward your face, or out from your computer screen (the direction of the current), your fingers will curl in a counter-clockwise direction.

Note that the right hand rule for a straight wire is different from the right hand rule for a planar magnetic field!

### Example Question #6 : Magnetism And Electromagnetism

A negatively charged particle is moving to the right along a vertical plane. If the force generated by a constant magnetic field is directed upwards within plane, in what direction is the magnetic field?

Downwards within the plane

Upward within the plane

Out of the plane, toward the observer

Out of the plane, away from the observer

Out of the plane, toward the observer

Explanation:

This question requires you to apply the right hand rule. Your thumb will point to the right, in the direction of the particle's velocity. For the negatively charged particle to feel an upward force, the back of your hand, not your palm as would be the case with a positively charged particle needs to be facing up. Extension of your fingers makes the magnetic field point out of the plane, toward you.

### Example Question #7 : Magnetism And Electromagnetism

A current of  runs through a straight wire. If the resulting magnetic field is , what is the radius of the field?

Explanation:

Ampere's law states:

.

In other words, the magnetic field (), is equal to a constant () times the current () divided by the circumference of the magnetic field it is creating.

We are given the current, the constant, and the magnetic field strength. Using these values, we can solve for the magnetic field radius.

Notice that the  cancels out.

### Example Question #1 : Electric Charge

Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as

Superconductors

Semiconductors

Insulators

Conductors

Conductors

Explanation:

Conductors allow the electrons to flow freely along it.  That is why metal; is considered a good conductor.  It allows the electrons to flow through it which is why it is used in wire in an an electric circuit.

### Example Question #2 : Electric Charge

A glass rod is rubbed with a piece of silk.  During the process the glass rod acquires a positive charge.  The silk

Acquires a negative charge

Remains neutral

Acquires a positive charge as well

Could either be positively charged or negatively charged.  It depends on how hard the rod was rubbed.

Acquires a negative charge

Explanation:

Since the glass rod acquires a positive charge, this means that it is deficient in electrons. Since the rod was rubbed by the piece of silk, the silk is what now collects the electrons.  The silk now has an excess of electrons which means that the silk is now negatively charged.

### Example Question #3 : Electric Charge

A charged rod carrying a negative charge is brought near two spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?

The spheres do not get any charge

The sphere near the charged rod becomes negative and the other becomes positive

The sphere near the charged rod becomes positive and the other becomes negative

None of these

The sphere near the charged rod becomes positive and the other becomes negative

Explanation:

When the negatively charged rod is brought near one of the two spheres, the presents of the negative charge will induce a flow of charge in the spheres such that regions farthest away from the charged rod will become most negative and regions near the rod will become most positive. This is called charge by induction.

### Example Question #4 : Electric Charge

By what method will a positively charged rod produce a negative charge on a conducting sphere that is placed on an insulating surface?

Charge by conduction

Charge by induction

None of these

Charge by convection

Charge by induction

Explanation:

Charge by induction happens when a charged object is brought in the vicinity of a neutral object. The presents of the charged object will cause the free charges in the neutral object to shift such that the neutral object becomes polarized. When the charged object is positive, this will induce a negative charge on a neutral object.

### Example Question #5 : Electric Charge

How many electrons make up a charge of ?