Physics Topic 12: Electromagnetic Induction

1. Derive the formula for the emf induced in a straight conductor moving in a magnetic field

If the rod is made to move ata speed v, it travels a distance of ?x = v?t. Therefore the area of the loopincreases by an amount ?A = l ?x = lv?t.

The emf induced is equal to the length of the conductor multiplied by the velocity of the conductor in the magnetic field.

The emf induced is equal to the product of the length of the conductor, the strength of the magnetic field, and the velocity of the conductor.

The emf induced is directly proportional to the strength of the magnetic field and inversely proportional to the velocity of the conductor.

2. Describe the production of an induced emf by a time changing magnetic flux.

Increased resistance in a circuit

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Decreased temperature in a conductor

A stagnant magnetic field

The production of induced emf by a time changing magnetic flux is a fundamental concept in electromagnetism involving Faraday's Law. It is not related to increased resistance, decreased temperature, or stagnant magnetic fields.

Explanation

The production of induced emf by a time changing magnetic flux is a fundamental concept in electromagnetism involving Faraday's Law. It is not related to increased resistance, decreased temperature, or stagnant magnetic fields.

3. Explain the operation of a basic alternating current (ac) generator

A generator only produces direct current (dc) and not alternating current (ac)

A generator consists of manyloops of wire wound on an armature that can rotate in a magnetic field. Theaxle is turned by some mechanical means and an emf is induced in the coil.

The generator uses permanent magnets to generate electricity

The rotation of the armature in a generator is caused by the flow of direct current

In a basic alternating current (ac) generator, the generation of electricity is achieved through the rotation of wire loops in a magnetic field, not through the use of permanent magnets or direct current. Additionally, generators can produce both direct current (dc) and alternating current (ac) depending on their design.

Explanation

In a basic alternating current (ac) generator, the generation of electricity is achieved through the rotation of wire loops in a magnetic field, not through the use of permanent magnets or direct current. Additionally, generators can produce both direct current (dc) and alternating current (ac) depending on their design.

4. Describe the effect on the induced emf of changing the generator frequency

Decreases the induced emf

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Increases the induced emf

Has no effect on the induced emf

The correct answer can be demonstrated through a visual aid or chart that shows the correlation between generator frequency and induced emf. This would help illustrate how changing the generator frequency influences the induced emf.

Explanation

The correct answer can be demonstrated through a visual aid or chart that shows the correlation between generator frequency and induced emf. This would help illustrate how changing the generator frequency influences the induced emf.

5. Discuss what is meant by the root mean squared (rms) value of an alternating current or voltage.

Rms values indicate the peak-to-peak value of the current or voltage.

Rms values are irrelevant in the context of alternating current or voltage.

Rms values are used to find the average voltage as they are sinusoidal

Rms values represent the maximum value of the current or voltage.

The root mean squared (RMS) value of an alternating current or voltage is crucial for determining the effective value of the signal. It is a method of finding the equivalent constant value of the alternating current or voltage that would produce the same amount of heat as the actual varying current or voltage over a given resistance.

Explanation

The root mean squared (RMS) value of an alternating current or voltage is crucial for determining the effective value of the signal. It is a method of finding the equivalent constant value of the alternating current or voltage that would produce the same amount of heat as the actual varying current or voltage over a given resistance.

6. State the relation between peak and rms values for sinusoidal voltage and currents.

Peak value = rms value / √2. Vpeak = Vrms / √2. Ipeak = Irms / √2.

Peak value = rms value x 2. Vpeak = Vrms x 2. Ipeak = Irms x 2.

Peak value = rms value x ,-2. Vpeak = Vrms x,-2.Ipeak = Irms x ,-2.

Peak value = rms value / 2. Vpeak = Vrms / 2. Ipeak = Irms / 2.

The relationship between peak and rms values for sinusoidal voltage and currents is that the peak value equals the rms value multiplied by the square root of 2. This relationship is crucial in understanding the conversion between peak and rms values in electrical systems.

Explanation

The relationship between peak and rms values for sinusoidal voltage and currents is that the peak value equals the rms value multiplied by the square root of 2. This relationship is crucial in understanding the conversion between peak and rms values in electrical systems.

7. Describe the operation of an ideal transformer

An ideal transformer uses mechanical gears to transform electrical energy

A useful device that makes use of electromagnetic induction is the ac transformer as it can be used for increasing or decreasing ac voltages and currents.

An ideal transformer operates solely on direct current (DC) power

An ideal transformer does not involve any electromagnetic principles to function

An ideal transformer makes use of electromagnetic induction to transfer electrical energy between two or more circuits without a change in frequency. It involves coils wrapped around magnetic cores that induce voltage in the secondary coil based on the turns ratio compared to the primary coil.

Explanation

An ideal transformer makes use of electromagnetic induction to transfer electrical energy between two or more circuits without a change in frequency. It involves coils wrapped around magnetic cores that induce voltage in the secondary coil based on the turns ratio compared to the primary coil.

8. Explain the use of high-voltage step-up and step-down transformers in the transmission of electrical power.

A step-up transformer decreases voltage from the power plant to the consumer's source.

An increased step-down voltage is necessary for greater power output.

Step-up transformers are used to reduce voltage in front of a house.

The voltage isstep-up from the power plant to have a higher power output due to powerdissipating. The voltage is then step-down when the power has reached itsconsumer source (where the power is being consumed). There is no ideal valve ofstep-up voltage due to economic reason. From the powerplant, a step-up transformer is used to increase voltage (so that current isdecreased) from 11,000 V to 250,000 V. from the transmission line to citystorage, a step-down transformer reduces voltage from 250,000 to 4500 V. thenin front of a house, a step-down transformer reduces that to 200-240V.

9. How do extra-low-frequency electromagnetic fields induce currents within a body?

A human body is aconducting medium, so when it is moving in an alternating magnetic field atextra-low-frequency, then electric field is induced, hence inducing current inhuman body.

Extra-low-frequency electromagnetic fields cause harm to the body's immune system.

Extra-low-frequency electromagnetic fields create a cooling effect on the body.

Extra-low-frequency electromagnetic fields have no effect on the human body.

When a human body moves in an alternating magnetic field at extra-low-frequency, an electric field is induced, which creates current within the body due to the conducting medium properties of the body.

Explanation

When a human body moves in an alternating magnetic field at extra-low-frequency, an electric field is induced, which creates current within the body due to the conducting medium properties of the body.