Terms in
current
1. current is the flow of electric
charge through a conductor
2. The standard international unit for
current (S.I) unit is ampere.
3. The symbol for current is I.
4. Metals or good conductors the current
is flow of electrons through the conductor.
5. In semiconductor current is the flow
of either negative electrons or positive holes.
6. Charge carriers are either electrons
or protons that current when flow through a conductor, in metals charge
carriers are electrons, in semiconductors charge carriers can be electrons or
holes.
7. An electric circuit is connection of
conductors that allow current to pass to pass through them.
8. A circuit is said to be closed when
current can pass through it.
9. A circuit is said to be open when
current cannot pass through. This means the current path is broken.
10.
A
conductor is a substance that readily allow the flow of current trough them. Examples
copper wire, iron etc.
11.
Semiconductors
are substances that allow few current to follow through them examples are
silicon.
12.
insulators
are substance that do not allow electric current to pass through them. examples
are rubber, wood.
13.
resistance
is the opposition or hindrance to the flow of electricity in a circuit.
14.
voltage
is the potential difference between two point when current pass through them.
15.
the
relationship between current voltage and resistance is given by ohm’s law. V=IR,
where I is the current in amperes, R is
the resistance in ohms and V is the voltage in volt.
16.
ampere
is the constant current that flow in two infinitely long, parallel, straight conductors
of negligible cross sectional area placed in a vacuum one meter apart . produce
between them a force of magnitudes 2X10-7N/m
17.
ohm,s
law states that the quantity of current flowing through a metallic conductor is
directly proportional to the potential different between its end, provided temperature
and pressure is constant.
18.
electric current is transmitted at high voltage low
current, the high voltage is to overcome the resistance, a current transmitted
at high current low voltage will be loss in form of heat.
19.
joule
heating or ohmic heating is the amount
of heat release when a current pass through a conductor.
20.
is
a plain representation of an electrical circuit. it show how electrical circuit
works.
21.
impedance
is opposition to the flow of A.C current in a circuit with either resistor and
capacitor, resistor and inductor r resistor with both.
22.
reactance
is the opposition to the flow of electric current in circuit with either resistor
or capacitor, when opposition is due to resistor only it is called capacitive
reactance and when it it is due to inductor only it is called inductive
reactance.
23.
impedance
and reactance only occur in alternating current circuit.
24.
alternating
current or A.C is a current that flow sinusoidally in reversed direction with
time. a.c current cannot be used in an appliances therefore rectifiers are
needed to change convert them to D.C.
25.
Rectification
is the changing of D.C to AC. rectifiers convert A.C current to D.C current,
rectifications are of two types, the half wave rectifiers and the full wave
rectifiers, in both half and full wave rectifiers current flow in one
direction.
26.
direct
current or D.C is the current that flow in the same direction.
27.
example
of full wave rectifiers are center tap rectifiers and bridge rectifiers, the
center tap has two diodes and a center tap transformer while the bridge has
four diode with no transformer.
28.
eddy
current are current that flow to opposes the magnetic flux that produced them.
29.
energy
band model explain why conductors conducts current readily, semiconductors
conduct electricity and insulators do not conduct current. in this model ,
there is no band gap between in conductors, the valence band and the conduction
are merged , in insulators the band gap is very narrow and little energy can
make insulators conduct current while the band gap in insulators have very wide
band gap.
30.
Current
density is amount of current flowing per unit cross sectional area of materials.
31.
1st
Kirchhoff’s law states that in any network of current the algebraic sum of all
current is zero.
32.
2nd
Kirchhoff’s law states that in a closed circuit the
algebraic sum of the product of current and resistance of all portion of the
circuit is equal to the sum of the electromotive force acting on the circuit.
33.
Resistivity
is the inverse of conductivity, it tells how a given material opposes the flow
of electric current, and it is proportional to length and inversely proportional
to the cross-sectional area of the material. Temperature increase resistivity.
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