Magnetism is a very nice

An electron is moving back and forth in a vacuum. What field/s is/are present?

• Electric field only

• Magnetic field only

• Both electric and magnetic fields

• No field exists since it is in a vacuum.

Answer explanation

An electron always creates an electric field. If it starts moving, it then creates a magnetic field since a magnetic field is created by a charged particle in motion.

Which statement about magnets is FALSE?

• Like poles repel.

• Poles can be isolated.

• They can exert a force.

• Field lines are from north to south.

Answer explanation

Unlike in electricity where charges can be separated, magnetic poles cannot exist on their own; they always come in pairs.

Where is the first magnet discovered?

• Magnesia

• Magnetes

• Magnetites

• Greece

Answer explanation

It is discovered in Greece, specifically in Magnesia, by a shepherd herding his sheep.

Refer to the given figure which shows a straight wire. If the current on the wire is directed to the right, what is the direction of the magnetic field at point P?

• To the left

• To the right

• Into the page

• Out of the page

Answer explanation

Using your right hand, point your thumb to the direction of the current which is to the right. If you curl your fingers, they curl toward you which is the direction of the magnetic field.

What happens to the magnetic field strength when measured nearer to the current-carrying wire than before?

• It increases.

• It decreases.

• It remains the same.

• More information is needed.

Answer explanation

As discussed, the magnitude of the magnetic field created by a current-carrying wire is inversely proportional to the distance from the wire. If you go near the wire, the magnetic field becomes stronger.

Refer to the given figure which shows the magnetic field created by the straight current-carrying wire. What is the direction of the current on it?

• To the left

• To the right

• Into the page

• Out of the page

Answer explanation

Curl your fingers such that it goes towards you from below then extend your thumb. Your thumb should be pointing to the left which is the direction of the current.

Which of the following factors, when increased, causes the magnetic field of the solenoid to decrease?

• Its length

• The current it has

• The number of loops it has

• None of the given choices

Answer explanation

As discussed, the magnetic field inside the solenoid is inversely proportional to its length.

A positively-charged particle is moving to the right where the magnetic field is pointed into the page. What is the direction of the magnetic force on it?

• Upward

• Downward

• To the right

• To the left

• No magnetic force

Answer explanation

Use your right hand. Point your index finger to the right then extend your middle finger into the page. Your thumb should be pointing upward.

A negatively-charged particle is moving downward where the magnetic field is pointed out of the page. What is the direction of the magnetic force on it?

• Upward

• Downward

• To the right

• To the left

• No magnetic force

Answer explanation

Use your left hand. Point your index finger downward then extend your middle finger out of the page. Your thumb should be pointing to the right.

A positively-charged particle is moving upward where the magnetic field is pointed downward. What is the direction of the magnetic force on it?

• Upward

• Downward

• To the right

• To the left

• No magnetic force

Answer explanation

Since the motion of the charged particle and the direction of the magnetic field are anti-parallel, there is no magnetic force.