38 Questions
What is the primary cause of inductance?
A changing magnetic field through a conductor
What type of waves are used in radio antenna applications?
Radio waves
How does an induction stove generate heat in a metal pot?
By generating a changing magnetic flux through the bottom of the pot
What is the purpose of a toroidal choke?
To partially choke off or restrict a sudden surge in current
What is the primary property of inductance?
It opposes changes in current
How does the presence of a soft iron cylinder affect the inductance of a toroidal choke?
It increases the inductance
What is the primary function of inductance in aviation antennas?
To detect very weak electromagnetic waves
How does inductance affect the change in current in an electrical circuit?
It tries to stop or delay the change in current
What is the main difference between a parallel circuit and a series circuit?
In a parallel circuit, the voltage is the same for all components, while in a series circuit the current is the same for all components.
What are the four main parameters required to analyze a parallel LCR circuit?
Reactance (both inductive and capacitive), branch currents, total circuit current, and phase angle.
How can you determine the total current (IT) drawn from the generator in a parallel LCR circuit?
By adding the branch currents together.
What is the relationship between the applied voltage and the branch currents in a parallel LCR circuit?
The applied voltage is the same for all components in the parallel circuit.
How can you determine the phase relationship between the total circuit current and the applied voltage in a parallel LCR circuit?
By constructing a phasor diagram to show the relationship between the branch currents.
What is the purpose of determining the reactance (both inductive and capacitive) in a parallel LCR circuit?
To analyze the branch currents in the circuit.
How does the total impedance of a parallel LCR circuit relate to the applied voltage and total current?
The total impedance is equal to the applied voltage divided by the total current.
What is the significance of determining whether a parallel LCR circuit is inductive or capacitive?
It indicates the phase relationship between the voltage and current.
What effect does an inductor have on a DC power source when connected in series with a resistor?
Opposes any change in current
Why is there no current flow in the circuit the instant the switch is closed?
Inductor opposes the change in current
What is induced in the inductor that helps oppose the supply voltage initially?
Back EMF
What happens to the current as the Back EMF in the inductor decreases?
Current decreases
What law remains true in a circuit with inductor and resistor connected to a power source?
Kirchhoff's Voltage Law
In what way do induction formulas differ from those for calculating resistance?
They are the same
What happens when a voltage sine wave is applied to a resistance in a circuit?
The resulting current is also a sine wave
When are two sine waves said to be in phase?
When they go through their maximum and minimum points at the same time and in the same direction
If two sine waves are in phase with each other, what can be said about their voltage drops and circuit current?
Their voltage drops and circuit current are in phase with each other
What is the condition for two AC power sources to be perfectly paralleled together?
They must be in phase with each other
What is the relationship between voltage and current in a resistance according to Ohm's law?
Current is directly proportional to the applied voltage
What is the phase difference between two sine waves that are 180 degrees out of phase?
180 degrees
If two voltage drops are in phase with each other, what can be said about their corresponding current sine waves?
Their current sine waves are also in phase with each other
What happens when two sine waves are out of phase with each other?
They go through their maximum and minimum points at the same time but in opposite directions
At higher frequencies, the parallel LCR circuit will be:
Capacitive
To calculate the total circuit current (IT) in a parallel LCR circuit, which formula is used?
$I_T = \sqrt{I_R^2 + (I_C - I_L)^2}$
Which formula is used to calculate the phase angle (θ) in a parallel LCR circuit?
$\tan \theta = \frac{I_L - I_C}{I_R}$
In a parallel LCR circuit, the reactive current is calculated as:
The difference between the inductive and capacitive currents
To calculate the reactance of an inductor (XL) in a parallel LCR circuit, which formula is used?
$X_L = 2\pi fL$
Which of the following is NOT a step in analyzing a parallel LCR circuit?
Calculating the total circuit resistance
To calculate the reactance of a capacitor (XC) in a parallel LCR circuit, which formula is used?
$X_C = \frac{1}{2\pi fC}$
In a parallel LCR circuit, the current through the resistor (IR) is equal to:
The voltage divided by the resistance
Study Notes
Inductance and Applications
- Inductance is the result of a voltage being induced in a conductor, produced by the conductor itself.
- Inductance has various applications, including:
- Radio antenna: used to detect electromagnetic waves
- Induction stove: generates heat in a metal pot using changing magnetic flux
- Toroid choke: restricts sudden surges in current using CEMF induced by a changing magnetic flux
Definition and Property of Inductance
- Inductance can be defined as the property of an electrical circuit that opposes any change in current.
- If current increases, the induced current tries to stop or delay that increase.
Series and Parallel Inductors
- Inductors can be arranged in series or in parallel to achieve desired results.
- Induction formulas for series and parallel connected inductors are similar to those for calculating resistance.
Voltage/Current Relationship
- An inductor has a significant impact on a DC power source.
- When a switch is closed, there is initially no current flow due to the inductor's opposition to change in current.
- As the back EMF reduces, the current will increase, and Kirchhoff's voltage law will still be true.
Parallel LCR Circuits
- In a parallel LCR circuit, the supply voltage appears across each component.
- The four main parameters required to analyze the circuit are reactance, branch currents, total circuit current, and phase angle between applied voltage and branch currents.
Determining Reactance in Parallel LCR Circuits
- In a parallel LCR circuit, the applied voltage appears across each component, even if there are multiple AC power sources that are in phase.
- Sine waves can be in phase with each other, having the same maximum and minimum points at the same time and direction.
Summary of Parallel LCR Circuit Analysis
- To analyze a parallel LCR circuit, calculate:
- Reactances (XL and XC)
- Current through each component (IR, IC, and IL)
- Equivalent reactive current (difference between IC and IL)
- Total circuit current (IT) and phase angle using SOH-CAH-TOA.
Test your knowledge on inductance and its applications in various devices such as radio antennas, aviation Australia antennas, and induction stoves. Learn about how inductance is the result of induced voltage in a conductor due to a magnetic field produced by the conductor itself.
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