Understanding Electromagnetic Induction

What is the formula for magnetic flux?

• Φ = B + A + θ

• Φ = B · A · cos(θ)

• Φ = B - A · sin(θ)

• Φ = B / A

Answer explanation

The formula for magnetic flux (Φ) is given by Φ = B · A · cos(θ), where B is the magnetic field strength, A is the area, and θ is the angle between the magnetic field and the normal to the surface. This choice correctly represents the concept.

State Faraday's Law of Induction.

• The induced EMF is equal to the sum of the magnetic fluxes in the circuit.

• The induced EMF is constant regardless of the magnetic flux change.

• The induced EMF is directly proportional to the magnetic field strength.

• The induced EMF is equal to the negative rate of change of magnetic flux through the circuit.

Explain Lenz's Law in your own words.

• Lenz's Law indicates that all currents flow in the same direction regardless of magnetic changes.

• Lenz's Law explains how magnetic fields can be created without any current.

• Lenz's Law describes how induced currents oppose changes in magnetic flux.

• Lenz's Law states that induced currents enhance changes in magnetic flux.

Answer explanation

Lenz's Law states that when a change in magnetic flux occurs, the induced current will flow in a direction that opposes that change. This means it acts to counteract the effect of the changing magnetic field.

What is the equation for induced emf due to motion?

• emf = B / (L * v)

• emf = B + L + v

• emf = B * v^2

• emf = B * L * v

Answer explanation

The induced emf due to motion is given by the equation emf = B * L * v, where B is the magnetic field strength, L is the length of the conductor, and v is the velocity. This relationship shows how motion through a magnetic field generates emf.

Define self-inductance.

• Self-inductance refers to the resistance of a coil to any change in voltage across it.

• Self-inductance is the ability of a coil to store electrical energy without any current change.

• Self-inductance is the process by which a coil generates heat when current flows through it.

• Self-inductance is the ability of a coil to induce an electromotive force in itself due to a change in current.

Answer explanation

Self-inductance is the ability of a coil to induce an electromotive force in itself due to a change in current. This phenomenon occurs when the magnetic field around the coil changes, leading to a voltage that opposes the change.

What is the formula for self-induced emf?

How is energy stored in an inductor calculated?

Answer explanation

The energy stored in an inductor is given by the formula E = (1/2) * L * I^2, where L is the inductance and I is the current. This formula reflects how energy is proportional to the square of the current.

What does the variable 'L' represent in inductance equations?

• Inductance of a coil or circuit.

• Resistance in a circuit

• Capacitance of a capacitor

• Length of a wire

Answer explanation

In inductance equations, 'L' specifically represents the inductance of a coil or circuit, which quantifies its ability to store energy in a magnetic field. The other options refer to different electrical properties.

Explain the significance of the negative sign in the self-induced emf equation.

• The negative sign shows that the induced emf enhances the change in magnetic flux.

• The negative sign is irrelevant to the self-induced emf equation.

• The negative sign indicates a positive change in magnetic flux.

• The negative sign signifies that the induced emf opposes the change in magnetic flux.

Answer explanation

The negative sign in the self-induced emf equation, according to Lenz's Law, indicates that the induced emf opposes the change in magnetic flux, ensuring energy conservation in electromagnetic systems.

What factors affect the amount of energy stored in an inductor?

• Temperature (T) and magnetic field strength (B)

• Capacitance (C) and frequency (f)

• Inductance (L) and current (I)

• Resistance (R) and voltage (V)

Answer explanation

The energy stored in an inductor is determined by its inductance (L) and the current (I) flowing through it, as given by the formula E = 1/2 L I^2. Other factors like temperature and resistance do not directly affect energy storage.