The magnetic field due o the current in a long straight wire is 80 mu T at a dis
ID: 1612807 • Letter: T
Question
The magnetic field due o the current in a long straight wire is 80 mu T at a distance of 4.0 cm from the center of the wire. What is the current in the wire? A) 0.20 A B) 0.80 A C) 3.2 A D) 0.40 A E) 1.6 A A light ray in air enters water at an angle of incidence of 40 degree. What has an index of refraction of 1.33. The angle of refraction in the water is A) 29 degree. B) 1.33 degree C) 40 degree. D) 0.59 degree. E) 59 degree. The index of refraction of a certain medium is 1.5. What is the speed of light in that medium? A) 3.0 times 10^8 m/s B) 1.0 times 10^8 m/s C) 5.0 times 10^8 m/s D) 4.0 times 10^8 m/s E) 2.0 times 10^8 m/s A transformer changes the 10,000 V power line to 120 V. If the primary coil contains 750 turns, how many turns are in the secondary? A) 0 B) 2.1 times 10^4 C) 6.3 times 10^4 D) 3 E) 9 A 500-W device is connected to a 100-V power source. What current flows through this source? A) 50,000 A B) 1.6 times 10^18 electrons/s C) 20.0 A D) 5.00 A E) 200. mA A mirror with a focal length 20 cm has a 4.0 cm tall object placed 100 cm in front of it. What is the position of the image? A) 20 cm behind the mirror B) 20 cm in front of the mirror C) 25 cm behind the mirror D) 100 cm in front of the mirror E) 25 cm in front of the mirror A 4.0 mu F capacitor is connected in series with a 2.0 k Ohm resistor across a 20-V DC source and a switch. What is the time constant of this RC circuit? A) 18 ms B) 40 ms C) 12 ms D) 9.0 ms E) 80 msExplanation / Answer
13) n = c/v
v = c/n
v = 3*10^8/1.5 = 2*10^8 m/s
14) v1/v2 = n1/n2
n2 = n1*v2/v1
n2 = 9
15) p = v*i
i = p/v = 5 A
16) 1/f = 1/u+1/v
v = fu/u-f
v = 25 cm
behind the mirror
17) t = r*c = 8 ms
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