Electricity and Magnetism Test Review

An object is charged negatively if it has gained _________________.

• electrons

• protons

• neutrons

• positrons

Answer explanation

An object is charged negatively when it gains electrons. Electrons are negatively charged particles, so their addition results in a net negative charge. Protons and positrons are positively charged, while neutrons are neutral.

A ________________ is a device that converts mechanical energy to electrical energy.

• generator

• motor

• transformer

• battery

Answer explanation

A generator is a device that converts mechanical energy into electrical energy, making it the correct choice. In contrast, a motor converts electrical energy to mechanical energy, a transformer changes voltage levels, and a battery stores energy.

The ________________ hand rule is used to determine the direction of a magnetic field around a current-carrying wire.

• right

• left

• upward

• downward

Answer explanation

The right hand rule helps visualize the direction of the magnetic field around a current-carrying wire. When you point your thumb in the direction of the current, your fingers curl in the direction of the magnetic field, confirming 'right' is correct.

Locations in space where a charged object experiences a force are called ________________ fields.

• electric

• magnetic

• gravitational

• nuclear

Answer explanation

Locations in space where a charged object experiences a force are called electric fields. Electric fields are created by charged objects and influence other charges within the field.

Transformers are used to convert ________________ to ________________.

Answer explanation

Transformers are used to convert alternating current (AC) to different voltage levels, either stepping it up or stepping it down, depending on the application.

The flow of electric current in a wire is caused by a difference in ________________ energy.

• potential

• kinetic

• thermal

• chemical

Answer explanation

The flow of electric current in a wire is driven by a difference in potential energy. This potential difference, or voltage, causes electrons to move, creating an electric current.

Earth's magnetic field protects us from ________________.

• Earth's magnetic field protects us from solar and cosmic radiation.

• harmful UV rays from the sun.

• the greenhouse effect.

• global warming.

Answer explanation

Earth's magnetic field acts as a shield, protecting us from solar and cosmic radiation, which can be harmful to life. The other options, such as UV rays and global warming, are not directly mitigated by the magnetic field.

In terms of atomic structure, conductors have ________________ that can move easily.

• free electrons

• bound electrons

• neutrons

• protons

Answer explanation

In conductors, free electrons are not tightly bound to atoms, allowing them to move easily and conduct electricity. This is why the correct answer is 'free electrons', as opposed to bound electrons, neutrons, or protons.

The principle on which an electric motor works is ________________.

• The principle on which an electric motor works is electromagnetic induction.

• The principle on which an electric motor works is static electricity.

• The principle on which an electric motor works is thermoelectric effect.

• The principle on which an electric motor works is photoelectric effect.

Answer explanation

The principle on which an electric motor works is electromagnetic induction, which involves the generation of electric current through the motion of a conductor in a magnetic field, enabling the motor to convert electrical energy into mechanical energy.

In a generator, the ________________ rotates to produce electricity.

• armature

• stator

• commutator

• transformer