The core of a transformer is laminated to _______

The power dissipated in an ac circuit is 0 if the circuit is

AC is transmitted to distant places

In a step-down transformer

The resonant frequency of an LCR circuit occurs at a frequency equal to

Choose the currect matched pair

a. Purely resistive circuit phase factor 

b. Purely Inductive circuit phase factor 

c. Purely capacitive circuit phase factor 

Power factor is one for __________

For an LCR circuit with an ac source of, Angular frequency co,

a. Circuit will be capacitive if 

b. Circuit will be inductive if 

d. Current will be leading voltage if 

Alternating current cannot be measured by a DC ammeter because ……………

Power factor is unity at ________

The current through pure L or C, which dissipates no power is called

The ac can be converted into dc with the help of a rectifier while dc into ac with the help of an ………………

For an LCR circuit with an ac source of, Angular frequency co,

The basic principle behind a transformer is …………………

Choose the correctly matched pair

A capacitor blocks dc, but allows ac to pass. Why?

A transformer is a device to change the value of current or voltage of an ac source without a change in its frequency
a. is the principle of a transformer.
b. A transformer cannot work on DC. Why?

A 100Ω resistor is connected to a 220 V, 50 Hz ac supply.
a. What is the rms value of current in the circuit?
b. What is the net power consumed over a full cycle?

For a practical transformer, the efficiency is less than one.
a. What is the efficiency of a transformed
b. List some reasons for the power losses in a transformer?

A charged 30μF capacitor is connected to a 27 mH inductor. What is the angular frequency of free oscillations of the circuit?

The given figure shows an RC circuit.

a. Arrive at an expression for net voltage.
b. What is the phase difference between voltage an current?

The current in the LCR circuit is

a. What are the factors on which the current depends at resonance?
b. What is the condition for the maximum resonant current?

An LCR series, AC circuit behaves like a purely resistive circuit at resonance condition.
a. Obtain an expression for resonant frequency?
b. What is the net voltage across the inductor and capacitor at resonance?

The sharpness of resonance is measured by Co-factor of the circuit.
a. What is Q- factor?
b. Obtain an expression for Q-factor.
c. What is the Q-factor of an L&R series circuit?

Obtain the resonant frequency ω_r of a series LCR circuit with L = 2.0 H, C = 32 μF and R = 10Ω. What is the Q-value of this circuit?

There are four main reasons for the power loss in a transformer.
a. What are these four reasons?
b. How are these losses reduced? Explain.

A transformer is an a.c device which transfers electric power from one circuit to another.
a. transformer converts a low voltage at high current to a high voltage at low current, its number of turns of the secondary coil is then the number of turns in the primary coil.
b. What is meant by the Efficiency of a transformer?

A charged capacitor is allowed to discharge through an inductor.
a. What type of energy is stored in the capacitor?
b. What type of energy is stored in an inductor?
c. What is the current when a capacitor is introduced in an ac circuit?

a. What is resonance in an LCR circuit?
b. How can we increase current in a series LCR circuit at resonance for same as supply?
c. Q value of a good medium wave receiver must be approximately 100. Why?

For a transformer relation between primary to secondary voltage and number of turns is 
a. A power transmission line feeds input power at 2300 V to a stepdown transformer with its primary windings having 4000 turns. What should be the number of turns in the secondary in order to get output power at 230 V? 2
b. What is the voltage and current relationship between primary and sec-

A peak value of the voltage in a circuit V=10 sin00 πt is 10 V.
a. What is the r.m.s value?
b. What is the frequency of ac?

r.m.s value of emf and current related to peak value as  and 
a. What do you mean by RMS value of emf and current?
b. The mean value of AC current in half cycle is and in full cycle is

For tuning, the natural frequency ie, the frequency of free oscillations of the LC circuit should be equal to the frequency of the radio wave.
a. A radio can tune over the frequency range of a portion of MW broadcast: (800 KHZ to200 KHZ). If its LC circuit has an effective inductance of 200 η H, what must be the range of its variable capacity?
b. Draw a figure shows a part of the radio tuning circuit. If X_c > X_L, draw the phasor diagram.

An alternating voltage is shown in the figure. Answer the questions based on the voltage shown

a. What is the peak value of voltage?
b. What is the rms value of the voltage?
c. What is the frequency of the voltage?
d. Write the general equation of the voltage?

A voltage source is connected to an electrical component X as shown in the figure.

a. Identify the device X.
b. Which of the following equations can represent the current through the circuit?

c. Draw the phasor diagram for the circuit.

The current through fluorescent lights is usually limited using an inductor.
a. Obtain the relation i = i₂ sin (ωt – ) for an inductor across which an alternating emf v = v_m sin ω t is applied.
b. Why it is better to use an inductor rather than a resistor to limit the current through the fluorescent lamp?
c. When00 V DC source is connected across a coil a current ofA flows through it. When00 V, 50 Hz AC source is applied across the same coil only 0.5 A flows. Calculate the resistance and inductance of the coil.

Phasor diagram of a series LCR circuit is shown. V_R, V_L, and V_c represent the respective DO- potential difference across resistor, inductor, and capacitor and I represents the circuit current Answer the following questions based on the phasor diagram shown.

a. In the phasor diagram, two quantities have the same phase. Identify them.
b. Redraw the given phasor diagram and complete it to show the applied voltage.
c. Is the frequency applied to the circuit above or below the resonant frequency?

11V variable frequency ac source is applied to a circuit as shown in the figure. At a particular frequency, the voltage across the capacitor and inductor are found to be equal.(Given L = 0.38 H, C = 27 μF and R = 48Ω)
a. Write one practical application of the circuit shown.
b. Find the current through the circuit.
c. What is the frequency of the applied ac source?
d. How does, the circuit current change if the plates of the capacitor are
(i) brought closer
(ii) Moved away?

An alternating voltage is connected to a box with some unknown circuital arrangement as shown. The applied voltage and current through the circuit are measured as v = 80 sin cot volt and i.6 sin (ωt + 45°) ampere.
a. Does the current lead or lag the voltage?
b. Is the circuit in the box largely capacitive or inductive?
c. Is the circuit in the box at resonance?
d. What is the average power delivered by the box?

A friend from abroad presents you with a coffeemaker when she visited you. Unfortunately, it was designed to operate at10V line to obtain 960W power that it needs.
a. Which type of transformer do you use to operate the coffeemaker at 220V?
b. Assuming the transformer you use as ideal, calculate the primary and secondary currents.
c. What is the resistance of the coffee maker?

The figure shows a step-down transformer used in the line AC of 220 V to light up a bulb marked2 V, 30 W.
a. The soft iron core gets heated after some time. Why?

b. Calculate the number of turns of the coil in the winding connected to the bulb, if the other coil has 22000 turns.
c. Suggest a method to modify the core so that the heat produced in the core can be minimized.

A100 resistor is connected to a 220V, 50 Hz ac supply.
a. What is the rms value of current in the circuit?
b. What is the net power consumed over a full cycle?

a. What is the important property of the circuit shown?
b. How do L and C affect the property?

c. Which form of energy is stored in capacitor and inductor?

A series LCR circuit with R = 20Ω, L =.5 H and C = 35 μF is connected to a variable- frequency 200 V ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle?

A radio can tune over the frequency range of a portion of MW broadcast band: (800 kHz to200 kHz). If its LC circuit has an effective inductance of 200 pH, what must be, the range of its variable capacitor?