Test3Shih

# Test3Shih - Platt David – Quiz 2 – Due 10:00 pm –...

This preview shows pages 1–3. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Platt, David – Quiz 2 – Due: Oct 18 2005, 10:00 pm – Inst: Ken Shih 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points A variable resistor is connected across a con- stant voltage source. Which of the following graphs represents the power P dissipated by the resistor as a function of its resistance R ? 1. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 2. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 3. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 4. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 5. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 6. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 7. 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) cor- rect Explanation: The power dissipated in the resistor has several expressions P = E I = E 2 R = I 2 R , where the last two are simply derived from the first equation together with the application of the Ohm’s law. Since the resistor is connected to a constant voltage source E = constant P = E 2 R = constant R , tells us that the power is inversely propor- tional to the resistance P ∝ 1 R . 0 1 2 3 4 5 6 7 8 910 1 2 3 4 5 Resistance (Ω) Power(W) 002 (part 1 of 3) 10 points A rectangular loop consists of 333 closely wrapped turns of wire and has dimensions . 17 m by 0 . 25 m. The loop is hinged along the y-axis, and its plane makes an angle of θ = 12 ◦ with the x-axis. A uniform magnetic field of 0 . 85 T is di- rected along the x-axis and the current in the loop is 3 . 2 A in the direction shown. Platt, David – Quiz 2 – Due: Oct 18 2005, 10:00 pm – Inst: Ken Shih 2 x y z 1 2 ◦ B = 0 . 85 T B = 0 . 85 T . 17m . 2 5 m i = 3 . 2 A What is the magnitude of the torque ex- erted on the loop? Correct answer: 37 . 6536 N m. Explanation: Let : n = 333 , / = 0 . 17 m , w = 0 . 25 m , θ = 12 ◦ , B = 0 . 85 T , and I = 3 . 2 A . The field makes an angle of α = 90 ◦- θ with a line perpendicular to the plane of the loop, so the torque acting on the loop is τ = nB I A sin α = nB I / w sin α (1) = (333)(0 . 85 T)(3 . 2 A)(0 . 17 m)(0 . 25 m) × sin(90 ◦- 12 ◦ ) = 37 . 6536 N m . 003 (part 2 of 3) 10 points Assume that θ is measured in the positive direction; i.e. , clockwise (looking down from above) as shown in the figure. If the loop is at rest, the magnetic torque will 1. try to lift the loop along the y-axis. 2. try to make θ larger. correct 3. try to make θ smaller. 4. not affect θ . 5. None of these 6. try to lower the loop along the y-axis. Explanation: The right hand rule shows that torque tends to rotate the loop clockwise as viewed from above....
View Full Document

{[ snackBarMessage ]}

### Page1 / 100

Test3Shih - Platt David – Quiz 2 – Due 10:00 pm –...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online