Advertisements
Advertisements
Question
For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I2Z cos φ.
- Here, the power factor cos φ ≥ 0, P ≥ 0.
- The driving force can give no energy to the oscillator (P = 0) in some cases.
- The driving force cannot syphon out (P < 0) the energy out of oscillator.
- The driving force can take away energy out of the oscillator.
Options
a, b and c
a, b and d
b, c and d
c and d
Advertisements
Solution
a, b and c
Explanation:
As per question P = I2Z cos `phi`P = I2Z cos `phi`
Power factor cos `phi` = RZ cos `phi` = RZ
As R > 0 and Z > 0
So cos `phi` = RZ cos `phi` = RZ is positive ⇒ P > 0
APPEARS IN
RELATED QUESTIONS
A power transmission line feeds input power at 2200 V to a step-down transformer with its primary windings having 300 turns. Find the number of turns in the secondary to get the power output at 220 V.
The primary coil of an ideal step-up transformer has 100 turns and the transformation ratio is also 100. The input voltage and power are 220 V and 1100 W, respectively. Calculate the
(a) number of turns in secondary
(b) current in the primary
(c) a voltage across secondary
(d) current in secondary
(e) power in secondary
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. (a) Draw a circuit diagram to represent the process. (b) label the poles of the electromagnet.
Name the phenomenon ?
The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why.
The transformer is used in ______ current circuits.
What is the function of a transformer in an a.c. circuit? How do the input and output powers in a transformer compare?
A transformer is used to step up an alternating emf of 200V to 440V. If the primary coil has 1000 turns, calculate the number of turns in the secondary coil.
Can a transformer be used with direct current source? Give reason.
State the mathematical relation between a number of turns in the primary coil to a secondary coil in the step-up transformer.
Describe the construction and working of a transformer with a neat labelled diagram.
In a series resonant RLC circuit, the voltage across 100 Ω resistor is 40 V. The resonant frequency ω is 250 rad/s. If the value of C is 4 µF, then the voltage across L is
Mention the various energy losses in a transformer.
A transformer is used ______
A step-down transformer connected to an ac mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?
For what purpose are the transformers used?
In an ideal transformer, the turns ratio is \[\frac {N_p}{N_s}\] = \[\frac {1}{2}\]. The ratio Vs : Vp is equal to (the symbols carry their usual meaning) ______.
An ideal transformer converts 170 V a.c. to 1.70 KV a.c. to transmit a power of 3.4 KW. If primary coil has 500 turns then alternating current in secondary coil is ______.
