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SAFETY AND CONTROL DEVICES

A switch is used to start, stop or change the direction of the current in a circuit These are used to control current in electrical circuits

Switches

Most of them are meant to operate at certain times under certain conditions to perform very definite functions

Inductance

The primary aspect of the operation of a coil is its property to oppose any change in current through it. This property is called-----------------?
1. Transister
2. Capacitance
3. Inductance
If more turns are used on the coil, meter deflection is------------------ and is proportional to the number of turns (n) ?
1. Less
2. Greater
3. Constant
It opposes the rate of change of current flowing through it due to the build up of self-induced energy within its magnetic field ?
1. Saturation current
2. Inductor
3. Capacitance
It is a qualitative law that specifies the direction of induced current but says nothing about its magnitude ?
1. Lenz's law
2. Electromagnetic induction
3. Faraday’s law
Eddy currents flow in closed loops within conductors, in planes------------------- to the magnetic field ?
1. Horizontal
2. Perpendicular
3. Longitudinal
They are also used in electronic filters to separate signals of different frequencies ?
1. Transister
2. Resistors
3. Inductors
They are used to block ac while allowing dc to pass, designed for this purpose are called ---------------?
1. Transister
2. Chokes
3. Capacitor
The permeability of ferromagnetic materials is------------------, but depends on h ?
1. Not Constant
2. Constant
3. Decreases
Eddy currents are also called ------------------?
1. Foucault currents
2. Saturation current
3. Self-induction
It is also called a choke ?
1. Capacitance
2. Transister
3. Inductor

Magnetism

Heating or sudden shock will cause misalignment of the molecules, causing the strength of a magnet ?
1. Increase
2. Decrease
3. No effect
Where no more lines of force can be induced or introduced, the material is then said to be ?
1. Non magnetic
2. Charged
3. Saturated
Any substance, such as bismuth, having a permeability of less than one, is considered ?
1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic
Measure of opposition to the lines of force through a material, can be compared to the resistance of an electrical circuit ?
1. Reluctance
2. Inductance
3. Capacitance
Reluctance of soft iron, for instance, is……...Than that of air ?
1. Much lower
2. Higher
3. Equal
Nonferrous metals with a permeability greater than one, such as nickel and cobalt, are called ?
1. Diamagnetic
2. Para magnetic
3. Ferromagnetic
Ability of a magnet to hold its magnetism varies greatly with the type of metal and is known as ?
1. Resistivity
2. Retentively
3. Capacitance
When a wire contains many loops, it is called a ?
1. Wire
2. Cable
3. Coil
Standard unit of magnetomotive force is the ?
1. Ampere-turn (at)
2. Volt-turn (VT)
3. Voltage
Gilbert is defined differently, and is a…...Unit than the ampere-turn ?
1. Slightly higher
2. Very small
3. Slightly smaller