lilofun

07.05.2021 21:57 •  Физика

1. How much money you will spend per week for having a light bulb working in the apartment circuit with the voltage of 220V and the current of 0.5 A. (Consider that 1 kW*hour costs 125 sum).

A. 231 sum:

B. 2310 sum;

C. 23100 sum;

D. 231000 sum;

2. A light bulb is connected to the battery of some EMF equal to . Will the light bulb be dimmer or brighter if it will be reconnected to a new battery of !"# =3. By how much?

A. Three times brighter

B. Three times dimmer

C. Nine times brighter

D. Nine times dimmer

3. Determine the direction of the magnetic field (!"#) at point P, located at the square of edge length=l. (Hint:

look at the direction of currents)

A. to the right

B. upward

C. downward

D. to the left

4. The automobile light bulbs shown in the circuits here are identical(same). The battery connection which produces more brighter light (power) is ….

A) circuit 2.

B) circuit 1.

C) both the same

5. A surface has the area vector =3!+4! (!). What is the flux of a uniform electric field through the area if the field is =5!? (! and ! are the unit vectors).

A. 25 ∙ !/ B. 15 ∙ !/ C. 12 ∙ !/

D. 20 ∙ !/

6. A proton moves through a uniform magnetic field given by =3 (T). The proton(! =1.5×10" (N). Find ! (T). (Hint: cross product of vectors and Lorentz force)

A. 0.75

B. -0.157

C. 0.1875

D. -0.1875

7. We touch two objects(spheres) to each other, what will be the final charges of the each object?

A. =7.5

B. =5

C. =15

D. =10

8. The current in a 50 mH inductor changes with time as =5 !−3, where I is in amperes and t is in seconds. Find the magnitude of the “induced emf” at t = 2 s.

A. 850 V

B. 370 V

C. 0.37 V

D. 0.85 V

9. If a piece of wire is stretched by N times what happens to the resistance?

A. Increases as N B. Increases as !

C. Decreases as N D. Decreases as !

10. What is the maximum value of an AC voltage whose “rms” value is 220 V?

A. 310 V B. 220 V C. 440 V

D. 142 V

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