7476

Physics Alternating Current Level: Misc Level

When the frequency of an ac circuit is increased at constant coltage, the current increases and then decreases. Which combination of elements is most likely to comprise this circuit?

(a) resistors only

(b) inductors only

(c) capacitors only

(d) a combination of inductors and resistors

(e) a combination of inductors and capacitors


7475

Physics Alternating Current Level: Misc Level

When the frequency of an ac circuit is decreased, the current in the circuit increases.Which combination of elements is most likely to comprise the circuit?

(a) resistors only

(b) inductors only

(c) capacitors only

(d) capacitors and resistors

(e) inductors and capacitors


7474

Physics Alternating Current Level: Misc Level

A battery is used to drive a circuit. After a certain amount of time the current is zero amperes. When the same circuit is driven by an ac generator,the current is non-zero and alternates. Which combination of elements is most likely to comprise the circuit?

(a) resistors only

(b) inductors only

(c) capacitors only

(d) capacitors and resistors

(e) inductors and capacitors


7396

Physics Alternating Current Level: Misc Level

A 220 ohm resistor is connected an ac voltage source V=(150V*sin [2 PI (60 Hz) t]. What is the average power delivered to this circuit?

(a) 51 W

(b)110 W

(c) 280 W

(d)320W

(e) 550 W


4705

Physics Alternating Current Level: Misc Level

A ship lies at the bottom of the sea at 1.5 miles, what is the total pressure on the hull at that depth?


4243

Physics Alternating Current Level: Misc Level

A powerplant produces a certain amount of power at a certain voltage, the power is stepped up to a much higher voltage for transmission over long distances using a transformer then stepped down to a lower voltage before it enters your home. what is the purpose of this procedure?


4013

Physics Alternating Current Level: University

Draw wave form for average current if the voltage across a 5 micro F capacitor is as shown.

Question Diagram


4012

Physics Alternating Current Level: University

Transient Current
The capacitor is initially charced to 3V with polarity shown.
(a) Find the mathematical expressions for the voltage Vc and the current Ic when switch is closed.
(b) Sketch the wave forms for Vc and Ic.

Question Diagram


4011

Physics Alternating Current Level: University

Charging and Discharging of Capacitior
(a) Determine time constant.
(b) Write mathematical equation for voltage Vc following the closing  of switch.
(c) Determine Vc after one three and five constant.
(d) Write the equations for current Ic and VR
Sketch the wave form for Vc and Ic.

Question Diagram


3969

Physics Alternating Current Level: University

Transmission of Current
An ac generator produces 10 A of current at 400 V. The voltager is stepped up to 4500 V by an ideal transformer and transmitted a long distance through a power line of total resistance 30.
(a) How much power is lost in transformer?
(b)If the voltage were not stepped up how much power would be lost in transmission?
(c) From your answer above is it more advantageous to transmit power at high or low voltage? Explain why?
(d) Why would a transformer not work if the current was direct instead of alternating? Explain fully.

3968

Physics Alternating Current Level: University

Transformer
 Paul is experimenting with his new magic set. He has a thin insulated copper rod 1.0 m long with a mass of 50g. What minimum current must he put through the rod cause it to
(a) Float (=zero velocity) in a magnetic field of 1.0 T
(b) Accelerate upwards at 75 cm/s^2 in a magnetic field of 1.0 T.
(c) Is your answer to (a) greater than less than or the same as your answer to (b) ? Explain why.
(d) Suppose he wants to construct a 2.5 mT solenoid for other magnetic tricks. What length of wore would he  need for  a 10 cm diameter 20 cm long solenoid if he used a 100 mA current? Assume a constant  diameter for each turn of the solenoid.

3712

Physics Alternating Current Level: University

When the switch is closed describe what the two measuring devices connected in parrallel will display for you. ( use diagrams if necessary) will the output data change over time? and if it does will it ever stop?
(b) Open the switch after a few moments describe what the two measuring devices connected in parallel will be displaying use diagrams if necessary) will the output data change over time and if it does will it ever stop?

Question Diagram


3695

Physics Alternating Current Level: University

Transformers
A step - up transformer is designed to have an out put of 2200 V when the primary is connected across a 110-V source. If there are 80 turns in the primary how many turns are required on the secondary? If a load resistor across the secondary draws a current of 1.5 A, what is the current in the  primary?

3643

Physics Alternating Current Level: University

Transient current
A 20-micro F capacitor is discharged through a 5 -K Ohm resistor. The initial charge on the capacitor is 200 micro C. Sketch a graph of the current through the resistor as a  function of time. Label both axes with numbers and units. What is the initial power dissipated in the resistor? What is the total energy dissipated?

3609

Physics Alternating Current Level: University

Use calculus to show directly that if i (t) = I (sub m ) cos wt it follows that I (effective or rms) = I (sum m) square root of 2.

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