1: In the standing wave lab, the distance between two fixed ends of the string (

Question

1: In the standing wave lab, the distance between two fixed ends of the string (from the vibrator to the pulley) is 1.2 m. You can find the mode #3 at frequency 90 Hz. What is the frequency of foundation mode? 15 Hz 30 Hz 33 Hz 45 Hz

2: In the sound wave experiment, we know the speed of sound wave is about 340 m/s. When we use a fork with frequency at 400 Hz. On which distance of water level, we have highest possible to find a resonance. About 15 cm About 33 cm About 48 cm About 64 cm

3: To measure the electric permittivity, we use capacitor and the equation: C:=:rac{arepsilon_0A}{d}. We measure the capacitance C and distance We can obtain the permittivity by the slop from the linear fitting. In the process, if we set the value in y-axis is C. What is the value on x-axis. d 1/d A A/d

4: In the inductance experiment, we know the emf is zero when the magnet at the middle of the solenoid. Which description is correct at the moment ? The magnetic flux is zero at this moment The direction of magnetic field change at this moment. The magnetic field from the north pole and south pole cancel each other The changing of magnetic flux is zero

5: Suppose we have a resistor R1 = 10 ohm tied in series with a parallel combination of two resistors R2 = 10 ohm and R3 = 5 ohm. The battery supplies is 5 V. What is the current pass through R3? 0.125 A 0.2 A 0.25 A 0.375 A

Explanation / Answer

1. for a standing wave at mode n
v = lamda*f
lambda = 2*L/n
v = 2Lf/n
2*1.2*90/3 = 2*1.2*f/1
f = 30 Hz
2. f = 400 Hz
lambda = d*4/3
v = lambda*f
340 = 4d*400/3 = 64 cm apx
3. C = Ae/d
   plot on x axis = d/A
slope = e
4. The changing of magnetic flux is zero, hence emf produced = 0
5. V = IR
I = V/R = 5/(10 + (1/10 + 1/5)^-1) = 0.375 A

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