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Questions and Answers
What is the phenomenon of inducing an opposing emf in the secondary coil due to a change in current in the primary coil called?
What is the phenomenon of inducing an opposing emf in the secondary coil due to a change in current in the primary coil called?
- Electromagnetic induction
- Mutual induction (correct)
- Electromagnetic interference
- Self-induction
What is the constant of proportionality between the magnetic flux linked with the secondary coil and the current passing through the primary coil?
What is the constant of proportionality between the magnetic flux linked with the secondary coil and the current passing through the primary coil?
- Coefficient of mutual induction (correct)
- Coefficient of electromagnetic interference
- Coefficient of electromagnetic induction
- Coefficient of self-induction
What is the SI unit of mutual inductance?
What is the SI unit of mutual inductance?
- Tesla
- Henry
- Weber (correct)
- Ampere
What is the dependence of the magnetic flux linked with the secondary coil on the current passing through the primary coil?
What is the dependence of the magnetic flux linked with the secondary coil on the current passing through the primary coil?
What is the induced emf in the secondary coil dependent on?
What is the induced emf in the secondary coil dependent on?
What is the definition of 1 henry?
What is the definition of 1 henry?
What is the relationship between the magnetic flux linked with the secondary coil and the number of turns of the coil?
What is the relationship between the magnetic flux linked with the secondary coil and the number of turns of the coil?
What is the unit of mutual inductance in terms of Vs/A?
What is the unit of mutual inductance in terms of Vs/A?
What is the time taken for one complete cycle in the given problem?
What is the time taken for one complete cycle in the given problem?
What is the value of omega (ω) in the given problem?
What is the value of omega (ω) in the given problem?
What is the emf (ε₀) when the coil reaches its peak value?
What is the emf (ε₀) when the coil reaches its peak value?
What is the area of the coil in problem 44?
What is the area of the coil in problem 44?
What is the frequency of the AC generator in problem 45?
What is the frequency of the AC generator in problem 45?
What is the maximum current drawn from the generator in problem 45?
What is the maximum current drawn from the generator in problem 45?
What is the magnetic field strength in problem 46?
What is the magnetic field strength in problem 46?
What is the angular frequency (ω) in problem 46?
What is the angular frequency (ω) in problem 46?
What happens when the key (K) is pressed in Experiment 2?
What happens when the key (K) is pressed in Experiment 2?
What conclusion can be drawn from the coil-coil experiment (One loop is stationary)?
What conclusion can be drawn from the coil-coil experiment (One loop is stationary)?
According to Faraday's First Law, what induces an emf in a circuit?
According to Faraday's First Law, what induces an emf in a circuit?
What does the galvanometer show when the key is kept open or closed in Experiment 2?
What does the galvanometer show when the key is kept open or closed in Experiment 2?
Which phenomena are the experiments demonstrating?
Which phenomena are the experiments demonstrating?
What is directly proportional to the induced emf according to Faraday's Second Law?
What is directly proportional to the induced emf according to Faraday's Second Law?
How is the galvanometer connected in Experiment 3?
How is the galvanometer connected in Experiment 3?
According to Faraday’s First Law, what does the amount of induced emf depend upon?
According to Faraday’s First Law, what does the amount of induced emf depend upon?
What principle is a transformer based upon?
What principle is a transformer based upon?
Why is a transformer core laminated?
Why is a transformer core laminated?
Which type of source does a transformer work with?
Which type of source does a transformer work with?
What is the function of the primary coil in a transformer?
What is the function of the primary coil in a transformer?
Why does a transformer not work with a DC source?
Why does a transformer not work with a DC source?
What happens in a step-up transformer?
What happens in a step-up transformer?
In a transformer, why is the core made of soft iron?
In a transformer, why is the core made of soft iron?
In power transmission, why is a step-up transformer preferred over a step-down transformer for long distances?
In power transmission, why is a step-up transformer preferred over a step-down transformer for long distances?
What is the change in flux when the initial flux is 2 Wb and the final flux is 8 Wb?
What is the change in flux when the initial flux is 2 Wb and the final flux is 8 Wb?
What is the formula used to calculate the induced emf?
What is the formula used to calculate the induced emf?
What is the magnitude of the emf induced in a 560-turn coil with an area of $0.065 m \times 0.065 m$, placed in a magnetic field of 1.2 T, when rotated 90 degrees in 0.2 ms?
What is the magnitude of the emf induced in a 560-turn coil with an area of $0.065 m \times 0.065 m$, placed in a magnetic field of 1.2 T, when rotated 90 degrees in 0.2 ms?
If the magnetic flux through a coil of 50 turns decreases from $3 \times 10^{-2}$ Wb to 0 in 20 ms, what is the induced emf?
If the magnetic flux through a coil of 50 turns decreases from $3 \times 10^{-2}$ Wb to 0 in 20 ms, what is the induced emf?
What is the initial magnetic flux through a coil with 560 turns, an area of $0.065 m \times 0.065 m$, and a magnetic field strength of 1.2 T?
What is the initial magnetic flux through a coil with 560 turns, an area of $0.065 m \times 0.065 m$, and a magnetic field strength of 1.2 T?
What is the current in a coil with a resistance of 100 ohms if the induced emf is 75 V?
What is the current in a coil with a resistance of 100 ohms if the induced emf is 75 V?
A coil initially oriented such that its axis coincides with the magnetic field direction is then rotated 90 degrees. What is the final flux if the magnetic field is 1.2 T and the area of the coil is $0.065 m \times 0.065 m$?
A coil initially oriented such that its axis coincides with the magnetic field direction is then rotated 90 degrees. What is the final flux if the magnetic field is 1.2 T and the area of the coil is $0.065 m \times 0.065 m$?
What is the charge in a coil if the current is 0.75 A and the time is 20 ms?
What is the charge in a coil if the current is 0.75 A and the time is 20 ms?
Study Notes
Mutual Induction
- Mutual induction occurs when a change in current in the primary coil induces an opposing emf in the secondary coil.
- The magnetic flux (Φ) linked with the secondary coil is directly proportional to the current (i) in the primary coil: Φ = Mi, where M represents mutual inductance.
- Mutual inductance (M) is numerically equal to the magnetic flux linked with one coil when a unit current (1 A) flows through the other.
- For N turns, the induced emf (e) is given by Faraday’s law: e = -N(dΦ/dt) = -M(di/dt).
- The mutual induced emf depends on mutual inductance (M) and the rate of change of current (di/dt) but not on the magnitude of the current.
Unit of Mutual Inductance
- The SI unit of mutual inductance is henry (H), defined as 1 H when the rate of change of current (di/dt) is 1 A/s and induces a voltage (e) of 1 V in the secondary coil.
Examples of Calculations
- Given a mutual inductance of 1.25 H and a full cycle of time (T) as 0.040 s, the angular frequency (ω) can be calculated: ω = 2π/T = 157 rad/s.
- Induced emf when t = T is found using the formula ε₀ = ωNBA, yielding a value of 63.6 V.
- A coil with dimensions 20 x 20 cm² and 30 turns in a magnetic field of 1 T produces an approximate induced emf of 226 V at 30 rps.
Faraday's Laws of Electromagnetic Induction
- First Law: An emf is induced in a circuit when there is a change in magnetic flux through it.
- Second Law: The magnitude of the induced emf is directly proportional to the negative rate of change of the magnetic flux.
Transformer Operation
- A transformer consists of a soft iron core with two coils: the primary coil receives AC voltage, while the secondary coil outputs induced emf.
- Transformers only function with AC as it provides a changing magnetic flux, unlike DC, which only produces steady current and does not induce emf.
Types of Transformers
- Step-up transformers elevate voltage from low to high for applications like power transmission over long distances.
- The primary coil has fewer turns (Np < Ns), with higher voltage (Vp < Vs) and lower current (iP > iS).
Demonstrating Electromagnetic Induction
- Coil-Coil Experiment: Shows deflection in a galvanometer (G) when there is a change in magnetic flux due to pressing or releasing a key in the primary coil.
- Coil Movement Experiment: Movement of one coil (C2) relative to another stationary coil (C1) induces emf, as shown by galvanometer deflection.
Problem-Solving with Electromagnetic Induction
- Example problems illustrate the calculation of induced emf, current, and magnetic fields in various setups, reinforcing the principles of electromagnetic induction.
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Description
This experiment demonstrates the phenomenon of electromagnetic induction, where two coils are placed close to each other and connected to a battery and a galvanometer, showing deflections when the key is pressed and released.
