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Questions and Answers
What does Lenz’s Law state about the direction of the induced current?
What does Lenz’s Law state about the direction of the induced current?
- It enhances the changing magnetic field.
- It has no effect on the magnetic field.
- It changes randomly.
- It opposes the initial changing magnetic field. (correct)
The equation for electromotive force (emf) does not include the number of loops in a coil.
The equation for electromotive force (emf) does not include the number of loops in a coil.
False (B)
What is the relationship between input power and output power in a transformer?
What is the relationship between input power and output power in a transformer?
Power input equals power output.
The equation for the speed of light can be expressed as _____ = frequency × wavelength.
The equation for the speed of light can be expressed as _____ = frequency × wavelength.
What happens to the voltage when a transformer steps up the voltage?
What happens to the voltage when a transformer steps up the voltage?
Match the following terms with their descriptions.
Match the following terms with their descriptions.
A transformer consists of coils on the same side of an iron core.
A transformer consists of coils on the same side of an iron core.
In the equation for emf, the symbol ∆𝜱 represents the change in _____
In the equation for emf, the symbol ∆𝜱 represents the change in _____
What does magnetic flux measure?
What does magnetic flux measure?
When the magnetic field is parallel to the plane of the area, the magnetic flux density is at its greatest.
When the magnetic field is parallel to the plane of the area, the magnetic flux density is at its greatest.
What creates an electromotive force (voltage) in a conductor?
What creates an electromotive force (voltage) in a conductor?
Magnetic flux is measured in ______.
Magnetic flux is measured in ______.
According to Faraday's Law, what will happen when there is a change in the magnetic environment of a coil?
According to Faraday's Law, what will happen when there is a change in the magnetic environment of a coil?
Match the phenomenon with its method of electricity generation:
Match the phenomenon with its method of electricity generation:
Electromagnetic induction requires a constant magnetic field.
Electromagnetic induction requires a constant magnetic field.
The angle the magnetic field direction makes with the normal to the plane of the cross-sectional area is represented by ______.
The angle the magnetic field direction makes with the normal to the plane of the cross-sectional area is represented by ______.
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Study Notes
Magnetic Flux
- Represents the number of magnetic field lines passing through a closed surface, measuring the total magnetic field through a given area.
- Can be assessed for any surface area and orientation relative to the magnetic field direction.
- Magnetic Flux Density is given by: 𝜱 = 𝑩 𝑨⋅cos𝜽
- 𝜱: magnetic flux density (Weber, Wb)
- 𝑩: magnetic field strength
- 𝑨: cross-sectional area the field penetrates
- 𝜽: angle between the magnetic field direction and the area normal
- Maximum magnetic flux occurs when the magnetic field is perpendicular (cos 0 = 1).
- Minimum magnetic flux occurs when the field is parallel (cos 90 = 0).
Electromagnetic Induction
- The phenomenon of inducing electromotive force (voltage) in a conductor amid a changing magnetic field.
- Governed by Faraday’s Law: a change in magnetic environment induces a voltage in a coil.
- Induction can be caused by:
- Varying magnetic field strength
- Movement of magnets in relation to coils
- Movement of coils within or out of magnetic fields
- Rotating coils relative to magnets
- Key applications:
- Electrical generation from steam turbines powered by coal, wind, or nuclear energy.
- Induced electromotive force (emf) calculated using:
- 𝑒𝑚𝑓 = −𝑛 (∆𝜱/∆𝑡)
- 𝑛: number of coil loops
- ∆𝜱: change in magnetic flux
- ∆𝑡: change in time
- 𝑒𝑚𝑓 = −𝑛 (∆𝜱/∆𝑡)
- Lenz’s Law indicates that induced current opposes the initial magnetic field change, ensuring energy conservation.
Transformers
- Devices designed to increase (step-up) or decrease (step-down) voltage levels.
- Operate based on conservation of power: 𝑃𝑖𝑛 = 𝑃𝑜𝑢𝑡, where
- 𝑉𝑝 × 𝐼𝑝 = 𝑉𝑠 × 𝐼𝑠
- Use coils wrapped around an iron core to generate a magnetic field, allowing voltage transformation.
- The relationship between primary and secondary voltages can be defined as:
- 𝑉𝑝/𝑉𝑠 = 𝑛𝑝/𝑛𝑠
Electromagnetic Radiation
- Light propagates as transverse waves with oscillating electric and magnetic fields.
- All wavelengths exist on the electromagnetic spectrum.
- Inverse relationship between frequency and wavelength as defined by: 𝑐 = 𝜆𝑓
- 𝑐: speed of light
- 𝜆: wavelength
- 𝑓: frequency
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