Magnetism & EMI
Q. What is the effect of increasing the capacitance in a capacitor in an AC circuit on the current?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Current becomes zero
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Solution
Increasing the capacitance (C) decreases the capacitive reactance (X_C), which increases the current (I) in the circuit.
Correct Answer: A — Increases current
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Q. What is the effect of increasing the capacitance in an AC circuit on the capacitive reactance?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Capacitive reactance (X_C) is given by X_C = 1/(2πfC). Increasing capacitance (C) decreases X_C.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the capacitance in an AC circuit on the phase angle between voltage and current?
A.
Increases phase angle
B.
Decreases phase angle
C.
No effect
D.
Phase angle becomes 90 degrees
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Solution
Increasing capacitance decreases the phase angle between voltage and current in an AC circuit.
Correct Answer: B — Decreases phase angle
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Q. What is the effect of increasing the current in a coil on the magnetic field strength?
A.
Increases
B.
Decreases
C.
No effect
D.
Depends on the coil material
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Solution
Increasing the current in a coil increases the magnetic field strength, as the magnetic field is directly proportional to the current.
Correct Answer: A — Increases
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Q. What is the effect of increasing the current in a solenoid on the magnetic field inside it?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The magnetic field inside a solenoid is directly proportional to the current flowing through it. Therefore, increasing the current increases the magnetic field strength.
Correct Answer: A — Increases
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Q. What is the effect of increasing the current in a solenoid on the magnetic field strength?
A.
Decreases the magnetic field strength
B.
Increases the magnetic field strength
C.
Has no effect
D.
Reverses the magnetic field direction
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Solution
Increasing the current in a solenoid increases the magnetic field strength, as B is directly proportional to I.
Correct Answer: B — Increases the magnetic field strength
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Q. What is the effect of increasing the current in a solenoid on the magnetic field strength inside it?
A.
Increases the magnetic field strength
B.
Decreases the magnetic field strength
C.
No effect on the magnetic field strength
D.
Reverses the direction of the magnetic field
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Solution
According to Ampere's Law, increasing the current in a solenoid increases the magnetic field strength inside it.
Correct Answer: A — Increases the magnetic field strength
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Q. What is the effect of increasing the current in a wire on the magnetic field around it?
A.
Increases the magnetic field
B.
Decreases the magnetic field
C.
No effect on the magnetic field
D.
Reverses the direction of the magnetic field
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Solution
Increasing the current in a wire increases the magnetic field around it, as per the Biot-Savart Law.
Correct Answer: A — Increases the magnetic field
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Q. What is the effect of increasing the distance from a current-carrying wire on the magnetic field strength?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
According to the Biot-Savart Law, the magnetic field strength decreases with increasing distance from the current-carrying wire.
Correct Answer: B — It decreases
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Q. What is the effect of increasing the distance from a long straight conductor on the magnetic field strength?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
According to Biot-Savart Law, the magnetic field strength decreases with increasing distance from the conductor.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the distance from a long straight current-carrying wire on the magnetic field strength?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
According to the Biot-Savart Law, the magnetic field strength decreases with increasing distance from the wire.
Correct Answer: B — It decreases
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Q. What is the effect of increasing the distance from a long straight wire on the magnetic field strength?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
The magnetic field strength decreases with increasing distance from a long straight wire, following the inverse relationship with distance.
Correct Answer: B — It decreases
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Q. What is the effect of increasing the frequency of an AC source on the inductive reactance of a circuit?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
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Solution
Inductive reactance (XL) is given by XL = 2πfL, so increasing the frequency (f) increases the inductive reactance.
Correct Answer: C — It increases
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Q. What is the effect of increasing the frequency of the alternating current in an inductor?
A.
Inductive reactance decreases
B.
Inductive reactance increases
C.
Inductive reactance remains constant
D.
Inductive reactance becomes zero
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Solution
Inductive reactance (XL) is given by the formula XL = 2πfL, where f is the frequency. Thus, increasing frequency increases inductive reactance.
Correct Answer: B — Inductive reactance increases
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Q. What is the effect of increasing the frequency on the capacitive reactance?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Capacitive reactance X_C = 1/(ωC) decreases with increasing frequency.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the frequency on the impedance of a series RLC circuit?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on R, L, and C
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Solution
The impedance (Z) of a series RLC circuit depends on the values of resistance (R), inductance (L), capacitance (C), and frequency (f). As frequency increases, the inductive reactance increases and capacitive reactance decreases, affecting the total impedance.
Correct Answer: D — Depends on R, L, and C
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Q. What is the effect of increasing the frequency on the impedance of an inductor?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The impedance of an inductor (Z_L) increases with frequency, as Z_L = jωL, where ω = 2πf.
Correct Answer: A — Increases
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Q. What is the effect of increasing the number of turns in a coil on the induced EMF when the magnetic field changes?
A.
Induced EMF decreases
B.
Induced EMF remains the same
C.
Induced EMF increases
D.
Induced EMF becomes zero
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Solution
According to Faraday's law of electromagnetic induction, the induced EMF is proportional to the rate of change of magnetic flux and the number of turns in the coil. Increasing the number of turns increases the induced EMF.
Correct Answer: C — Induced EMF increases
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Q. What is the effect of increasing the number of turns in a coil on the induced EMF?
A.
It increases the induced EMF
B.
It decreases the induced EMF
C.
It has no effect
D.
It makes the EMF negative
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Solution
Increasing the number of turns (N) in a coil increases the induced EMF, as EMF = -N * (dΦ/dt).
Correct Answer: A — It increases the induced EMF
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Q. What is the effect of increasing the number of turns in a coil on the induced EMF when the magnetic flux changes?
A.
It increases the induced EMF
B.
It decreases the induced EMF
C.
It has no effect
D.
It makes the induced EMF zero
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Solution
According to Faraday's law, the induced EMF is directly proportional to the number of turns in the coil. Therefore, increasing the number of turns increases the induced EMF.
Correct Answer: A — It increases the induced EMF
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Q. What is the effect of increasing the number of turns in a coil on the magnetic field produced?
A.
Increases
B.
Decreases
C.
No effect
D.
Reverses
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Solution
Increasing the number of turns increases the magnetic field strength.
Correct Answer: A — Increases
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Q. What is the effect of increasing the number of turns in a coil on the magnetic field produced by it?
A.
It decreases the magnetic field
B.
It has no effect
C.
It increases the magnetic field
D.
It reverses the magnetic field direction
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Solution
Increasing the number of turns in a coil increases the magnetic field produced, as the field is proportional to the number of turns.
Correct Answer: C — It increases the magnetic field
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Q. What is the effect of increasing the number of turns in a solenoid on the magnetic field inside it?
A.
Magnetic field decreases
B.
Magnetic field remains constant
C.
Magnetic field increases
D.
Magnetic field becomes zero
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Solution
The magnetic field inside a solenoid is directly proportional to the number of turns per unit length. Increasing the number of turns increases the magnetic field strength.
Correct Answer: C — Magnetic field increases
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Q. What is the effect of increasing the radius of a circular loop carrying current on the magnetic field at its center?
A.
It increases the magnetic field
B.
It decreases the magnetic field
C.
It has no effect
D.
It reverses the direction of the magnetic field
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Solution
The magnetic field at the center of a circular loop is inversely proportional to the radius; thus, increasing the radius decreases the magnetic field.
Correct Answer: B — It decreases the magnetic field
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Q. What is the effect of increasing the radius of a circular loop on the magnetic field at its center?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The magnetic field at the center of a circular loop decreases as the radius increases.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the resistance in a series AC circuit?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Increases voltage
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Solution
Increasing the resistance in a series AC circuit decreases the current.
Correct Answer: B — Decreases current
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Q. What is the effect of increasing the resistance in a series RLC circuit on the Q factor?
A.
Increases Q factor
B.
Decreases Q factor
C.
No effect
D.
Doubles Q factor
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Solution
Increasing resistance decreases the Q factor, which is defined as Q = ωL/R.
Correct Answer: B — Decreases Q factor
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Q. What is the effect of increasing the resistance in an AC circuit on the overall current?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Doubles current
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Solution
According to Ohm's law, increasing resistance in an AC circuit decreases the overall current.
Correct Answer: B — Decreases current
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Q. What is the effect of increasing the speed of a charged particle moving in a magnetic field?
A.
Increases the magnetic force
B.
Decreases the magnetic force
C.
No effect on the magnetic force
D.
Reverses the direction of the force
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Solution
The magnetic force on a charged particle is proportional to its speed; increasing the speed increases the magnetic force.
Correct Answer: A — Increases the magnetic force
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Q. What is the effect of increasing the speed of a conductor moving through a magnetic field on the induced EMF?
A.
Increases the induced EMF
B.
Decreases the induced EMF
C.
No effect on the induced EMF
D.
Induced EMF becomes zero
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Solution
According to Faraday's law, the induced EMF is directly proportional to the rate of change of magnetic flux, which increases with speed.
Correct Answer: A — Increases the induced EMF
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