Advertisements
Advertisements
प्रश्न
A device ‘X’ is connected to an a.c source. The variation of voltage, current and power in one complete cycle is shown in figure.
- Which curve shows power consumption over a full cycle?
- What is the average power consumption over a cycle?
- Identify the device ‘X’.
Advertisements
उत्तर
(a) Power is the product of voltage and current (Power = P = VI).
So, the curve of power will be having a maximum amplitude, equal to the product of amplitudes of voltage (V) and current (I) curve. Frequencies, of B and C are equal, therefore they represent V and I curves. So, curve A represents power.
(b) The full cycle of the graph (as shown by the shaded area in the diagram) consists of one positive and one negative symmetrical area.
Hence, average power consumption over a cycle is zero.
(c) Here phase difference between V and I is π/2 therefore, the device ‘X’ may be an inductor (L) or capacitor (C) or the series combination of L and C.
APPEARS IN
संबंधित प्रश्न
Show that the current leads the voltage in phase by π/2 in an AC circuit containing an ideal capacitor ?
When an AC source is connected to a capacitor, there is a steady-state current in the circuit. Does it mean that the charges jump from one plate to the other to complete the circuit?
A current i1 = i0 sin ωt passes through a resistor of resistance R. How much thermal energy is produced in one time period? A current i2 = −i0 sin ωt passes through the resistor. How much thermal energy is produced in one time period? If i1 and i2 both pass through the resistor simultaneously, how much thermal energy is produced? Is the principle of superposition obeyed in this case?
Is energy produced when a transformer steps up the voltage?
A transformer is designed to convert an AC voltage of 220 V to an AC voltage of 12 V. If the input terminals are connected to a DC voltage of 220 V, the transformer usually burns. Explain.
An AC source producing emf ε = ε0 [cos (100 π s−1)t + cos (500 π s−1)t] is connected in series with a capacitor and a resistor. The steady-state current in the circuit is found to be i = i1 cos [(100 π s−1)t + φ1) + i2 cos [(500π s−1)t + ϕ2]. So,
The peak voltage of a 220 V AC source is
A bulb rated 60 W at 220 V is connected across a household supply of alternating voltage of 220 V. Calculate the maximum instantaneous current through the filament.
The dielectric strength of air is 3.0 × 106 V/m. A parallel-plate air-capacitor has area 20 cm2 and plate separation 0.10 mm. Find the maximum rms voltage of an AC source that can be safely connected to this capacitor.
A transformer has 50 turns in the primary and 100 in the secondary. If the primary is connected to a 220 V DC supply, what will be the voltage across the secondary?
Suppose the initial charge on the capacitor is 6 mC. What is the total energy stored in the circuit initially? What is the total energy at later time?
A.C. power is transmitted from a power house at a high voltage as ______.
A capacitor has capacitance C and reactance X, if capacitance and frequency become double, then reactance will be ______.
An alternating current of 1.5 mA and angular frequency 300 rad/sec flows through a 10 k Ω resistor and a 0.50 µF capacitor in series. Find the rms voltage across the capacitor and impedance of the circuit.
When an AC voltage of 220 V is applied to the capacitor C ______.
- the maximum voltage between plates is 220 V.
- the current is in phase with the applied voltage.
- the charge on the plates is in phase with the applied voltage.
- power delivered to the capacitor is zero.
Explain why the reactance provided by a capacitor to an alternating current decreases with increasing frequency.
A resistor of 50 Ω, a capacitor of `(25/pi)` µF and an inductor of `(4/pi)` H are connected in series across an ac source whose voltage (in volts) is given by V = 70 sin (100 πt). Calculate:
- the net reactance of the circuit
- the impedance of the circuit
- the effective value of current in the circuit.
