Answer: R = 394.36ohm
Explanation: In a LR circuit, voltage for a resistor in function of time is given by:

ε is emf
L is indutance of inductor
R is resistance of resistor
After 4s, emf = 0.8*19, so:





R = 394.36
In this LR circuit, the resistance of the resistor is 394.36ohms.
Answer:
ε = 6.617 V
Explanation:
We are given;
Number of turns; N = 40 turns
Diameter;D = 18cm = 0.18m
magnetic field; B = 0.65 T
Time;t = 0.1 s
The formula for the induced electric field(E.M.F) is given by;
ε = |-NAB/t|
A is area
ε is induced electric field
While N,B and t remain as earlier described.
Area = π(d²/4) = π(0.18²/4) = 0.02545
Thus;
ε = |-40 × 0.02545 × 0.65/0.1|
ε = 6.617 V
(we ignore the negative sign because we have to take the absolute value)
Answer: The amplitude is 0. (assuming that the amplitude ot both initial waves is the same)
Explanation:
When two monochromatic light waves of the same wavelength and same amplitude undergo destructive interference, means that the peak of one of the waves coincides with the trough of the other, so the waves "cancel" each other in that point in space.
Then if two light waves undergo destructive interference, the amplitude of the resultant wave in that particular point is 0.