Science

12. galvanizingity
? Current
I?

Q
t

I ? sure
Q ? net change string uping
t ? time

?

building block: The unit of current is ampere
Q ? Coulomb (C)
I ? Ampere (A)

1A ?

1C
1s

t ? Second (s)

? Potential difference
? The potential difference between ii separate depicts is defined as the work done to
relocation a unit positive charge from one point to another.
V?

W
Q

? Unit: The unit of potential difference is Volt
1 Volt ?

1 joule
1 coulomb

1 V ? 1 J C ?1

? Ohms law
? Current ? potential difference
V?I
V = IR

(R = resistance)

? Unit (R) ? ? (Ohm)
1? ?

1V
1A

? Factors on which resistance depends
o R ? l,

when A and material constant l = length

o R ? 1/A, when l and material constant A = perpendicular cross-section
R?

l
A

R??

l
A

( ? = resistivity)

? Resistivity: Resistivity of a substance is equal to the resistance of a unit second power of
that substance.

Unit ( ? ) ?? m
? Resistance in a series connection
R = R1 + R2 + R3 + … + Rn
? Resistance in parallel
11
1
1
??
? ...



?
R R1 R2
Rn

? Heating Effect of current
Electric energy = VIt
Heat, H ? VIt
? I 2 Rt

? Application
Electric iron, toaster, consolidated wire
Fused wire: a low-melting point wire machine-accessible in series with electric devices for
safety.
? Electric power
V2
P ? VI ? I R ?
R
2

? Unit 1 kWh = 3.6 × 106 J
1 W = 1V × 1A
? Ohm law: Under constant physical conditions (i.e., constant temperature, pressure
etc.), the current preying through a conductor is directly relative to the potential
difference across the conductor.
? Potential difference (which is measured in Voltage) is the cause of current (which is
measured in Ampere).
? In conductors, flow of electrons constitute current. In a circuit current flow from
positive terminal of the bombardment to the prejudicious terminal, but electrons travels from
negative terminal to the positive terminal. The negative terminal of a battery is said to
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