Electricity 4 Flashcards
define heating effect of electric current
the production fo heat energy in a conductor due to the flowing of electric current through it is called heating effect of electric current.
justify the heating effect of current
a metallic conductor contains a large amount of free electrons. When connected to a source of electrical energy like a dry cell or bettery, these free electrons begin drifitng from the negative terminal to the positive terminal of the cell/battery. During this travel, they collide with each other and with the walls of the conductor. This makes them to lose their kinetic energy, This lost kinetic energy is observed as heat.
how is the energy from the cell used?
A part of
the source energy in maintaining the current may be consumed into
useful work (like in rotating the blades of an electric fan). Rest of the
source energy may be expended in heat to raise the temperature of
gadget
what does joules law give us?
H = I2Rt
This is known as Joule’s law of heating. The
law implies that heat produced in a resistor is
(i) directly proportional to the square of current
for a given resistance, (ii) directly proportional to
resistance for a given current, and (iii) directly
proportional to the time for which the current flows
through the resistor.
why is the bulb filled with a gas inert at room temperature?
The filament of the bulb is enclosed with glass envolope. The glass envolope is filled with an unreactive gas like nitrogen or argon in order to increase the life of the tungsten filament.
what is electric fuse?
-electric fuse is a safety device connected in series with a circuit or electrical appliance.
- it is made of a wire made of a material whose melting point is very low.ex: aluminium, iron, tin-lead alloy
-based on heating eff of current
explain mechanism of a fuse
when a large amount of current flows through a circuit and hence the fuse wire, a large amount of heat is produced due to heating effect of current.This large amount of heat will cause the fuse wire to melt due to its low melting point. The fuse wire melts and breaks the electric circuit preventing the large amount of current from flowing in the circuit. The fuse then saves the electrical appliance from burning.
explain fuse rating
electrical fuses used in an electric circuit has rating 1A, 2A, 3A, 5A etc. This means that the maximum amount of current that can flow through the fuse without it melting is 1A. If a current more than 1A passes through the fuse, the fuse wire will melt and the circuit will melt.
define electric power
electric power refers to the amt of electrical energy dissipated or consumed per unit time.
electric power is the rate at whcih electrical energy is consumed y an appliance
p=e/t
define the si unit of power
The SI unit of electric power is watt (W). It is the power consumed by
a device that carries 1 A of current when operated at a potential difference
of 1 V. Thus 1 W = 1 volt × 1 ampere = 1 V A
units of watt
1kW= 1000 W
1MW=1000000 W
1GW=1000000000W
I horespower= 746 W
what is electrical energy? hwo does department measure it
electrical energy= electrical power x time
the department of eelctricity sells electric energy in units called kilowatt-hour.
1unit= 1kWh
define 1kWh
1 kilo-watt hour refers the amount of electrical energy consumed when a 1000W appliance operates for 1 hour.It is also called Board of Trade Unit.
give the relation between commercial and traditional unit of joule
1 kWh= 1kW x 1h
I 1Kw= 1000W
1h= 60 x 60= 3600s
1kWh= 1000 x 3600
= 3.6 x 10⁻⁶ J
define electrical energy
it refers to the work done by a source of electricity to maintain electric current in a source of electricity.
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