AP Physics Electricity & Magnetism — Questions and Answers

Question 1: What is Ohm's Law?

V = I/R
V = I * R (Correct answer)
V = I + R
V = R * I

Correct answer: V = I * R

Ohm's Law is a fundamental principle in electrical circuits that describes the relationship between voltage (V), current (I), and resistance (R). The formula V = I * R states that the voltage across a conductor is directly proportional to the current flowing through it, with the constant of proportionality being the resistance. This law is crucial for analyzing and designing electrical circuits.

Question 2: What does a capacitor do in an electrical circuit?

It stores and releases energy (Correct answer)
It resists the flow of current
It generates electricity
It decreases resistance

Correct answer: It stores and releases energy

A capacitor is an electrical component specifically designed to store electrical energy in an electric field between two conductive plates separated by a dielectric material. It can then rapidly release this stored energy back into the circuit, acting like a temporary battery or a filter to smooth out voltage fluctuations. This ability to store and release energy is vital for many electronic applications.

Question 3: How does a magnetic field affect a moving charge?

It increases the velocity
It exerts a force perpendicular to motion (Correct answer)
It changes the charge
It stops the motion

Correct answer: It exerts a force perpendicular to motion

When a charged particle moves through a magnetic field, it experiences a magnetic force. A key characteristic of this force is that it is always perpendicular to both the direction of the particle's velocity and the direction of the magnetic field. This perpendicular force causes the particle to change its direction of motion, often resulting in a curved path, but does not change its speed.

Question 4: What is the unit of electrical resistance?

Joule
Volt
Ohm (Correct answer)
Ampere

Correct answer: Ohm

The Ohm (Ω) is the SI unit of electrical resistance, named after Georg Simon Ohm, who formulated Ohm's Law. Resistance quantifies how much a material opposes the flow of electric current. According to Ohm's Law, one ohm is defined as the resistance between two points of a conductor when a potential difference of one volt produces a current of one ampere.

Question 5: What is the function of an inductor in an electrical circuit?

It stores electrical energy
It resists changes in current (Correct answer)
It decreases voltage
It generates electricity

Correct answer: It resists changes in current

An inductor is a passive electrical component that stores energy in a magnetic field when electric current flows through it. Its primary function is to resist changes in the current flowing through it, a property known as inductance. This resistance to current change helps to smooth out current fluctuations, filter signals, or create specific timing delays in various electrical circuits.

Question 6: What is a common characteristic of series circuits?

Voltage is the same across all components
Current is the same through all components (Correct answer)
Resistance is the same across all components
Power is the same across all components

Correct answer: Current is the same through all components

In a series circuit, all components are connected end-to-end, forming a single, uninterrupted path for the electric current. Consequently, the same amount of current must flow through each and every component in the circuit, as there are no alternative branches or paths for the current to take. This is a defining characteristic that distinguishes series circuits from parallel circuits.

Question 7: What does a battery do in an electric circuit?

It resists the current flow
It provides voltage (Correct answer)
It generates energy from the circuit
It decreases current

Correct answer: It provides voltage

A battery acts as a source of electromotive force (EMF) in an electric circuit. It creates a potential difference, or voltage, across its terminals, which provides the necessary electrical 'pressure' to drive the flow of electrons and thus the current through the circuit. This voltage enables the circuit to do work.

Question 8: What is the relationship between current, voltage, and power in an electrical circuit?

P = I / V
P = I + V
P = I * V (Correct answer)
P = V / I

Correct answer: P = I * V

The relationship between current, voltage, and power in an electrical circuit is fundamental. Electrical power (P) is defined as the rate at which electrical energy is transferred or converted. It is directly proportional to both the current (I) flowing through the circuit and the voltage (V) across it, expressed by the formula P = I * V.

Question 9: How is electrical energy related to power?

E = P * t (Correct answer)
E = P / t
E = P + t
E = P - t

Correct answer: E = P * t

Electrical energy (E) is the total amount of work done or energy consumed over a period. Power (P) is the rate at which this energy is transferred or consumed. Therefore, to calculate the total energy, you multiply the power by the time (t) for which it was applied, resulting in the equation E = P * t.

AP Physics Electricity & Magnetism

What is Ohm's Law?