Unit 19 Electricity Flashcards
In an atom the electrons
are attracted to the protons
An open circuit is one in which
a switch is open
Ohms law can be stated as
E=IR
3 devices that are capable of generating an electromotive force
photocells chemical reaction (battery) mechanically driven generator
The electrical pressure that causes electrons to flow through a circuit
Electromotive force
A unit of electrical resistance
Ohm
A unit of electrical power
Watt
A mechanical device used to open and close an electrical circuit
a switch
A unit of electrical current flow
Ampere
A device that is place in an electric circuit which melts to protect the circuit form overloading
Fuse
The difference in voltage between one end of a wire and the other ( or between any two points)
Potential Difference
A unit of electrical pressure
Voltage
Three resistors of 50, 40 and 20 ohms respectively are connected in parallel to an electrical supply. If the current flowing through the 20 ohm resistor is 5 amperes
Determine:
a. the supply voltage
b. the current flowing through the 50 and 40 ohm
c. the total line current
The relationship between the resistance and a change in length of the conductor
The resistance varies directly with the change of length. (if the length is doubled the resistance is doubled)
The relationship between diameter and resistance
if the diameter is doubled, the resistance is reduced 4 times
the unit of work
joule
formula for electrical power
P= IE
The total number of lines of force in a magnetic field determine the value of the
flux or flux density
two metals that do not have magnetic properties
silver and copper
Describe the relationship between an electric current flowing through a conductor and the magnetic field around a conductor
Whenever an electric current is passed through a conductor, a circular magnetic field is produced around the conductor, and the direction of the magnetic field is dependent on the direction of the current flow
Name and describe the rule used to determine the direction of a magnetic field around a single conductor
The right hand rule is used to mentally grasp the conductor with the thumb pointing in the direction of the current flow. the fingers then point in the direction of the magnetic field.
How is the magnetic field affected when a current carrying conductor is wrapped into a coil
The magnetic field is reinforced and increased by each wrap of the wire in the coil
The sum of the magnetic lines of force about a magnet
Magnetic flux
The space around a magnet through which the magnetic lines of flux are considered to travel
Magnetic field
What is the phenomenon discovered by Michael Faraday
When a conductor is moved across a magnetic field, an electric current is induced in the conductor
Describe the right hand rule for generators
thumb and first 2 fingers of the right hand. Thumb points in the direction of motion, the index points in the direction of the magnetic lines of force, second finger indicates the direction of induced current flow.
The purpose of a rectifier is to
Change AC voltage to DC
3 methods to increase the voltage generated as a conductor is passed through a magnetic field
Increase the speed the lines of force are cut
Increase the strength of the magnetic field
Increase the number of conductors
When a generator is used to produce electric current and the generator uses a commutator, the voltage will be
Direct Current
State the basic principle of motor action that occurs with a current carrying conductor when placed in a magnetic field
When conductor carrying a current is placed in an magnetic field, the conductor tends to move in a direction at right angles to the field.
what is the left hand rule for motors
determines the direction of the force exerted on an current carrying conductor placed in a magnetic field. Thumb, index, and middle finger held at 90degrees to each plane. The index finger represents the direction of the magnetic flux, second finger represent the direction of current flow, and the thumb indicates the direction of the force acting on the conductor
