Electricity and Magnetism Review Flashcards

Magnetism Practice

• Homework: Magnetism Review, due Thursday

• Additional Evidence due on Final Day

• Magnetism Practice on Monday, May 19, 2025

• Magnetism Review on Tuesday, May 20, 2025

• Magnetism Assessment on Next Tuesday

• Magnetism Assessment on Thursday, May 22, 2025

Learning Objectives

• Understand Earth's magnetic field and how it affects compass behavior.

• Explain how electric currents create magnetic fields and apply this to electromagnets.

• Understand how magnetism can be induced by electric current and how current can be induced by changing magnetic fields.

• Observe and explain the basic principles behind the operation of a simple electric motor.

• Review key concepts of magnetism and apply them to solve problems in a practice test

• Complete targeted practice assignments to demonstrate additional evidence of understanding and improve proficiency

• Earth as a Magnet

• The Earth is a large magnet.

• The Earth’s magnetic south pole is within 200 miles of the Earth’s geographic north pole.

Earth's Magnetic Field and Solar Wind

• The Sun and the Earth are connected.

• Earth possesses a magnetic field extending into space.

• This field is compressed by solar wind.

• The magnetic field deflects much of the solar wind around the Earth.

• Without the magnetic field, solar wind would damage the atmosphere.

• Plasma, the fourth state of matter, contains ions and/or free electrons and conducts electricity.

Electricity vs. Magnetism

Key Relationships Between Electricity and Magnetism

1. Moving charges or electric currents generate magnetic fields.

2. A changing magnetic field induces an electric current.

3. Magnetic fields exert a force on moving charges or electric currents.

Solenoid

• A long, straight coil of wire can generate a nearly uniform magnetic field, similar to a bar magnet.

• This coil is called a solenoid.

• The magnetic field is concentrated and nearly uniform inside a long solenoid.

• The field outside is weak and divergent.

• Right-hand rule applies.

Electromagnetic Induction

• Henry and Faraday discovered that moving a wire in a magnetic field induces a current.

• An electric current is generated when a wire cuts across magnetic field lines.

• A steady magnetic field does not produce current; only a changing magnetic field does.

Magnetic Fields Produced by Moving Charges or Current

• Right-hand rules predict the direction of magnetic fields produced by conventional current flow.

• Use the left hand to predict the direction of movement for an electron or negative charge.

Magnetic Force on Moving Charges

• A moving charged particle (like a proton or electron) creates a magnetic field.

• If the charge moves through an external magnetic field, the magnetic fields interact, resulting in attraction or repulsion.

• The force is perpendicular to the direction of the charge and the direction of the magnetic field (Lorentz Force).

Magnetic Force on Current-Carrying Wires

• Electric current through a wire creates a magnetic field.

• If the current moves through an external magnetic field, the magnetic fields interact, resulting in attraction or repulsion.

• The force is perpendicular to the direction of the current and the direction of the magnetic field.

• Right-hand rules apply.

Generators and Alternating Current

• Magnetic flux changes through an area if the field strength or direction changes.

• Rotating a permanent magnet near a wire loop, or vice versa, changes the magnetic flux through the loop.

• This change in flux produces an electromotive force (emf), causing current to flow in the loop.

• This setup is an electric generator.

• Generators convert mechanical energy into electrical energy.

• The emf produced by a generator is alternating (AC).

Motors

• When electric current passes through a coil in a magnetic field, the magnetic force produces torque.

• This torque turns the DC motor.

Transformers

• The function of a transformer is to change the voltage so that it suits the needs of a particular application.

• The ratio of the number of turns on the two coils determines the ratio of the voltages.

• The ratio of the number of turns on the two coils determines the ratio of the voltages.This means that if the primary coil has more turns than the secondary coil, the transformer will step down the voltage, whereas if the secondary coil has more turns, it will step up the voltage.

Additional Evidence Assessment

• Focus on physics skills where you can demonstrate improved understanding.

• Use past assessments, notes, and practice tests to guide review.

• Choose the assignment(s) to complete for the Additional Evidence Assessment.

• Show all work for math problems in your notebook.

Equations

Magnetic force follows the inverse square law, just like electric force.