A wire rod rolls with a speed of 20 m/s on two metallic rails, 1.0 m apart, that

Question

A wire rod rolls with a speed of 20 m/s on two metallic rails, 1.0 m apart, that form a closed loop. If the magnetic field is 1.5 T onto the page, the power dissipated in the resistor R and the current direction are, respectively, A) 33 mw, clockwise. B) 33 mW, counterclockwise. C) 76 mW, counterclockwise. D) 76 mw, clockwise. E) 50 mW, clockwise. How much does the maximum EMF produced by a generator (a rotating coil) change if the area of the coil is quadrupled? A) it is the same B) it is increased by a factor of sixteen C) it is increased by a factor of eight. D) it is increased by a factor of four E) it is impossible to tell given the information provided You place a 50-mH inductor across an AC generator that has a maximum EMF of 120 V. The inductive reactance when the frequency is 60 Hz is approximately A) 3.0 Ohm B) 0.31 Ohm C) 6.0 Ohm D) 47 Ohm E) 19 Ohm A series RLC circuit is driven by a 1.0-kHz oscillator. The circuit parameters are V_rms = 12 V, L = 5.0 mH, C = 4.0 mu F, and R = 10 Ohm. Under these conditions the current A) lags the voltage by 40 degree. D) leads the voltage by 57.1 degree. B) leads the voltage by 40 degree. E) None of these are correct. C) lags the voltage by 57.1 degree. Which of the following statements is true? A) Maxwell's equations apply only to fields that are constant in time. B) Electromagnetic waves are longitudinal waves. C) The electric and magnetic fields are out of phase in an electromagnetic wave. D) The electric - and magnetic fields vectors E vector and B vector are equal in magnitude in an electromagnetic wave. E) None of these statements is true. A 60-W light bulb emits spherical electromagnetic waves uniformly in all directions. If 50% of the power input to such a light bulb as electromagnetic radiation, what is the radiation intensity at a distance of 2.00 m from the light bulb? A) 15 W/m^2 B) 4.8 w/m^2 c) 2.4 W/m^2 D) 0.60 W/m^2 E) 1.2 W/m^2

Explanation / Answer

5. P = B^2 L^2 v^2 / R

P = (1.5^2) (1^2)(20^2) / (11.8 x 10^3)

P = 76 x 10^-3 W or 76 mW

I -> clockwise

Ans(D)

6. Em = N A B w

now A is quadrupled so EMF will also quadrupled.

Ans(D)

7. XL = 2 pi f L

= 2 x pi x 60 x 0.05

= 18.8 ohm

Ans(E)

8. XL = 2 x pi x 1000 x 0.005 = 31.4 ohm

Xc = 1/ (2 x pi x 1000 x 4 x 10^-6) = 39.8 ohm

theta = tan^-1[ (XL - Xc) / R] = - 40 deg

theta is -ve so current leads voltage.

Ans(B)

9. (B)

10. P = 0.50 x 60 = 30 W

I = P / (4 pi r^2)

= 30 / (4 x pi x 2^2)

= 0.6 W/m^2

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