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Questions and Answers
What is the function of the commutator in a DC generator?
What is the function of the commutator in a DC generator?
- To provide a path for the current to flow.
- To regulate the speed of the generator.
- To increase the voltage of the output current.
- To convert AC to DC. (correct)
How does a microphone convert sound waves into an electrical signal?
How does a microphone convert sound waves into an electrical signal?
- By changing the resistance of a material in response to sound pressure variations.
- By using a piezoelectric crystal that vibrates in response to sound pressure variations.
- By using an optical sensor that detects changes in light intensity caused by sound waves.
- By using a fixed magnet and a coil that moves in response to sound pressure variations. (correct)
What is the primary function of a transformer?
What is the primary function of a transformer?
- To convert AC to DC.
- To regulate the flow of current.
- To amplify the power of electrical signals.
- To increase the voltage of AC signals. (correct)
What would happen if a DC current were applied to the primary coil of a transformer?
What would happen if a DC current were applied to the primary coil of a transformer?
Why does a step-up transformer increase the voltage of the secondary coil?
Why does a step-up transformer increase the voltage of the secondary coil?
What is the effect on the induced current if the speed at which a coil rotates in a magnetic field is increased?
What is the effect on the induced current if the speed at which a coil rotates in a magnetic field is increased?
Which of the following is NOT a factor affecting the size of the current induced in a generator?
Which of the following is NOT a factor affecting the size of the current induced in a generator?
A coil of wire is moved through a magnetic field. What happens to the induced current if the coil is moved faster through the field?
A coil of wire is moved through a magnetic field. What happens to the induced current if the coil is moved faster through the field?
What is the purpose of the turbine in a power station?
What is the purpose of the turbine in a power station?
How does the magnetic field produced by the induced current in a wire moving in a magnetic field interact with the original magnetic field?
How does the magnetic field produced by the induced current in a wire moving in a magnetic field interact with the original magnetic field?
Which of the following is true about the current produced by a generator?
Which of the following is true about the current produced by a generator?
A wire loop is placed in a magnetic field. What happens to the loop if the magnetic field strength is increased?
A wire loop is placed in a magnetic field. What happens to the loop if the magnetic field strength is increased?
In a simple generator, how is the current induced in the coil?
In a simple generator, how is the current induced in the coil?
If the power of a transformer is 100%, what is the relationship between the power in the primary circuit and the power in the secondary circuit?
If the power of a transformer is 100%, what is the relationship between the power in the primary circuit and the power in the secondary circuit?
Why are high voltages used to transmit electrical energy over long distances?
Why are high voltages used to transmit electrical energy over long distances?
What is the purpose of a step-down transformer in the domestic power supply?
What is the purpose of a step-down transformer in the domestic power supply?
What is the relationship between the number of coils on the primary and secondary sides of a transformer and the voltage ratio?
What is the relationship between the number of coils on the primary and secondary sides of a transformer and the voltage ratio?
Why is it essential to reduce the voltage of electricity before it reaches our homes?
Why is it essential to reduce the voltage of electricity before it reaches our homes?
If the number of coils on the primary side of a transformer is 100 and the number of coils on the secondary side is 20, what is the voltage ratio (Vp/Vs)?
If the number of coils on the primary side of a transformer is 100 and the number of coils on the secondary side is 20, what is the voltage ratio (Vp/Vs)?
Which of the following statements is TRUE about the relationship between voltage and current in a transformer with 100% efficiency?
Which of the following statements is TRUE about the relationship between voltage and current in a transformer with 100% efficiency?
What is the primary function of a step-up transformer in the national grid?
What is the primary function of a step-up transformer in the national grid?
Flashcards
Current Induction
Current Induction
Current is induced when a wire moves through a magnetic field.
Potential Difference
Potential Difference
A difference in electric potential that causes electrons to move in a conductor.
Induced Current
Induced Current
Current flows if the conductor is part of a circuit during induction.
Opposition of Fields
Opposition of Fields
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Small-scale Generation
Small-scale Generation
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Large-scale Generation
Large-scale Generation
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Factors affecting Current/Voltage
Factors affecting Current/Voltage
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Alternator vs. Dynamo
Alternator vs. Dynamo
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Commutator
Commutator
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Direct Current (DC)
Direct Current (DC)
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Microphone function
Microphone function
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Transformer function
Transformer function
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Step-up transformer
Step-up transformer
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Step-down transformer
Step-down transformer
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Transformer equation
Transformer equation
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National Grid
National Grid
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High voltage advantage
High voltage advantage
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Power relationship in transformers
Power relationship in transformers
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Voltage and current relationship
Voltage and current relationship
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Efficiency in energy transmission
Efficiency in energy transmission
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Study Notes
Electromagnetic Induction
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Current Induction: A current is induced if a wire moves in a magnetic field. The conductor creates a potential difference, and if connected in a circuit, a current flows. The induced current's magnetic field opposes the original change.
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Production (Small-Scale): Spinning a wire coil in a magnetic field creates a small current, detectable with a sensitive ammeter. Passing a wire through a magnetic field also induces a current.
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Production (Large-Scale): Power stations use steam turbines, driven by combustion or nuclear fission, which turn coils of wire in a magnetic field to generate large currents (generators).
Factors Affecting Induced Current
- Number of Coils: More coils produce a larger current.
- Speed of Rotation: Faster rotation means a larger current.
- Magnetic Field Strength: A stronger magnetic field produces a larger current.
Alternators
- Alternating Current (AC): The current switches direction every half-turn. A commutator is not needed.
- Mechanism: The coil rotates in a magnetic field. The direction of the induced current reverses with each half-turn.
Dynamos
- Direct Current (DC): The current flows in one direction. A commutator reverses the current every half-turn.
- Mechanism: Same setup as an alternator, but a commutator ensures a continuous flow in one direction.
Microphones and Loudspeakers
- Mechanism: Sound waves cause a coil to vibrate within a magnetic field, inducing a proportional current. This current can drive a loudspeaker, which produces sound through its cone movements.
Transformers
- Alternating Current (AC) Necessity: Transformers only work with alternating current (AC) to produce a changing magnetic field.
- Step-Up Transformers: Increase voltage by having more coils on the secondary coil than primary.
- Step-Down Transformers: Decrease voltage by having fewer coils on the secondary coil than primary.
- Relationship: Voltage ratio is proportional to the number of coils ratio. The power in the primary is equal to the power in the secondary.
- National Grid: High voltages are used to transfer energy between power stations efficiently over long distances across the national grid.
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