Unit 14: Magnetic Induction Flashcards
What determines the polarity of magnetism when current flows through a conductor?
The direction of the current flow determines the polarity of the magnetic field.
What determines the strength of the magnetic field when current flows through a conductor?
The amount of current determines the strength of the magnetic field.
Name three factors that determine the amount of induced voltage in a coil.
- The number of turns of wire
- The strength of the magnetic field (flux density)
- The speed of the cutting action
How many lines of magnetic flux must be cut in 1 s to induce a voltage of 1 V?
One volt is induced in a conductor when magnetic lines of flux are cut at a rate of 1 weber per second. One weber equals 100,000,000 lines of flux.
What is the effect on induced voltage of adding more turns of wire to a coil?
Increased inductance. The amount of inductance an inductor will have is determined by the number of turns of wire and the physical construction of the coil.
Into how many time constants is an exponential curve divided?
An exponential curve is divided into five time constants.
Each time constant of an exponential curve is equal to what percentage of the maximum amount of charge?
Each time constant is equal to 63.2% of some value.
An inductor has an inductance of 0.025 H and a wire resistance of 3 Ω. How long will it take the current to reach its full Ohm’s law value?
The time necessary for current in an inductor to reach its full Ohm’s law value is called the R-L time constant.
.025 H / 3 Ω = .008 s
Assume that the inductor has a wire resistance of 0.2 Ω and the resistor has a value of 250 Ω. If a current of 3 A is flowing through the inductor, what will be the maximum induced voltage when the switch is opened?
0.992 x 3 A = 2.976 A
What electronic component is often used to prevent large voltage spikes from being produced when the current flow through an inductor is suddenly terminated?
Two devices used to help prevent large spike voltages are the resistor and the diode.
