Electric current
●》 the electric current is a flow of electric charge in a conductor such as metal wire.
● the si unit of electric current is ampere.
Which is denoted by letter A.
Electric currentt = Charge/time. Or I=Q/t.
●》 1 ampere :- when one coulomb of charge flows through any cross section of a conductor in 1 second the current flowing through it is said to be1 ampere.
1 ampere = 1Coulomb/1 second. Or 1 A= 1c/1 s.
● current is measured by an instrument called ammeter.
Q. An electric bulb draws a current of 0.25A for 20 minutes. Calculate the amount of electric charge that flows through the circuit.
Solution:- I= 0.25A
Q=? , t = 20 min.
= 20×60 seconds
= 1200 s
I = Q/t
0.25= Q/1200
Q= 0.25×1200C
Q=300 C.
Hence, the amount of electric charge flow through the circuit is 300 C.
Ohm's law
●》 this law states that the current passing through a conductor is directly proportional to the potential difference across its end, provides the physical conditions like temperature density etc remains unchanged.
I is directly proportional to V or I =1/R×V or V=IR.
R is called resistance of the conductor.
●》 Resistance =
Potential differences/ conductor.
Or R=V/I
1 ohm = 1 volt / 1 ampere.
●》 factors on which resistance of a conductor depends: The resistance R of a conductor depends on its length l, breadth b and the area of cross section A and the nature of its material.
R= p L/A.
● the proportionality constant p is called resistivity of the conductor.
●》 Joules law of heating:- it states that the heat produced in a conductor is directly proportional to the (1). square of current I through it, (2). its resistance R and(3). the time for which current is passed.
Mathematically, it can be expressed as
H=I^2Rt joule =I^2Rt/4.18 cal
H= vit joule= Vit/4.18 cal
P=W/t =VI =I^2 R = V^2/R
● Electric power efficiency = output power/ input power.
Resistance in series, Rs = R1+R2+R3+......
Resistance in parallel, 1/Rp= 1/R1 +1/ R2+1/R3+.......
Woe so helpful
ReplyDelete