What is the relationship between voltage drops and current in a resistive AC circuit?
For resistors in AC circuits the direction of the current flowing through them has no effect on the behaviour of the resistor so will rise and fall as the voltage rises and falls. The current and voltage reach maximum, fall through zero and reach minimum at exactly the same time.
What is the phase relation between voltage and current?
So at any instant in time we can say that the phase of voltage, v will be the same as the phase of the current, i. Then the angle of rotation within a particular time period will always be the same and the phase difference between the two quantities of v and i will therefore be zero and Φ = 0.
What is the phase relation between current and voltage in an inductor?
Answer. The phase relationship between current and voltage in an AC circuit containing only inductor is that voltage always leads the current flowing through the circuit by 90 degree or pi/2 radians. When a sinusoidal input is provided to the circuit, the current increases from zero to the maximum value.
What is the relationship between current and voltage in inductor?
Inductor voltage is proportional to change of current When we learned about resistors, Ohm’s Law told us the voltage across a resistor is proportional to the current through the resistor: v = i R v = i\,\text R v=iRv, equals, i, start text, R, end text.
What is the phase difference between current and voltage in inductor?
Phase Angles Current lags voltage by 90° in an inductor.
What is the phase difference between the voltage across inductor and capacitor?
Answer: In the interaction of capacitors or inductors in an AC circuit, the current and voltage do not peak at the simultaneously. That fraction of difference in the period between the peaks expressed in degrees is said to be the phase difference. The phase difference is <= 90 degrees.
Why choke is preferred to a resistor in an AC circuit?
Ans: A choke coil is an inductance which provides reactance (xL) which is equal to 2fL, where f is the frequency of a.c. source and L be the self inductance of the coil. Hence to control the current without making much power loss, we prefer a chock coil to rheostat/ resistor in an a.c. circuit.
Why choke coil is preferred to reduce current in a circuit rather than a resistor?
A choke coil is preferred over resistances in a.c. circuit because a choke coil has large value of self inductance and hence, the power dissipation is 0 for choke coil. 1 there will be no effect on the flow of current as resistance is independent of frequency.
What is the best method of reducing current in an AC circuit and why?
To reduce current in an ac circuit,a choke coil is preferred over a resistance. This is so because.
Why choke coil has high inductance and low resistance?
A choke coil has high inductance and low resistance , due to large inductance L of the coil, the current in the circuit is decreased appreaciably. Due to small resistance of the coil , the power loss in the choke , coil is less.
What is the principle of choke coil?
The choke’s impedance increases with frequency. Its low electrical resistance passes both AC and DC with little power loss, but its reactance limits the amount of AC passed. The name comes from blocking—”choking”—high frequencies while passing low frequencies.
What is the power factor of a good choke coil?
The correct option (a) Nearly zero Explanation: Power factor of good choke coil is nearly zero as phase difference ɸ between voltage & current is almost 90°. ∴ cos ɸ = 0.
How do you find the power factor of a coil?
This therefore gives us: Power Factor = Real Power/Apparent Power, or p.f. = W/VA. Then the cosine of the resulting angle between the current and voltage is the power factor. Generally power factor is expressed as a percentage, for example 95%, but can also be expressed as a decimal value, for example 0.95.
What is the meaning of power factor in electricity?
Power factor (PF) is the ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA). It is found by multiplying (kVA = V x A). The result is expressed as kVA units. PF expresses the ratio of true power used in a circuit to the apparent power delivered to the circuit.
What action is taken if power factor is less than or exceeds this range?
Poor power factor means you need to draw more power from the electricity networks to do the same work, and the cables need to be larger so it’s going to cost more. If the power factor become too low then the electricity supplier might charge you a penalty fee or reactive power charge.
What is an acceptable power factor?
The ideal power factor is unity, or one. Anything less than one means that extra power is required to achieve the actual task at hand. All current flow causes losses both in the supply and distribution system. A load with a power factor of 1.0 results in the most efficient loading of the supply.
What are the causes and disadvantage of low power factor?
Disadvantages of low power factor At low power factor, the current is high which gives rise to high copper losses in the system and therefore the efficiency of the system is reduced. Higher current produced a large voltage drop in the apparatus. This results in the poor voltage regulation.
What are the causes and effect of poor power factor?
The major effect of poor power factor is higher value of line current. For a given power and voltage, the current flowing through the line is inversely proportional to the power factor. This means that a poor power factor i.e. low power factor will result in higher load current and hence higher losses.
What is the meaning of poor power factor?
A power factor of less than one indicates the voltage and current are not in phase, reducing the average product of the two. In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred.