Ohm’s Law

Question 1 State ohm’s law?

Question 2 What is the resistance of an electric arc lamp, if the lamp uses 20 A when connected to a 220 Volt line?

Question 3 Define resistance of a conductor. What is its SI unit?

Question 4 Write the formula which relates electric current, time and electric current?

Question 5 What kind of plot would you expect when current is plotted against potential difference?

Question 6 What happens to the resistance as the conductor is made thinner?

Question 7 What is the SI unit of resistance?

Question 8 What is the use of rheostat?

Question 9 Define the term variable resistance?

Question 10 What is a good conductor?

Question 11 What is a bad conductor?

Question 12 What are insulators?

 

Ohm’s Law

George Simon ohm(in 1826)studied relationship between I and V across the ends of conductor.

Ohm’s Law states that electric current flowing in a conductor is directly proportional to potential difference across the ends of the conductor, provided temperature and other physical conditions remains constant.

V=IR

R=Resistance of conductor

Resistance of a conductor is the property of conductor to oppose the flow of charge through it.

R = V/I

Unit of resistance is ohm

1 ohm =  1 Volt / 1 Ampere

Resistance of a conductor is said to be 1 ohm if a potential difference of 1 volts across the ends of conductor makes a current of 1 ampere to flow through it.

 

Slope = I / V

Slope of graph V and I=Resistance of a conductor

V=IR

I= V/R

If R is halved then I is doubled.

If R is doubled then I is halved.

In an electric circuit, sometimes current has to be increase or decrease. A component used in an electric circuit to change the current without changing the potential difference across the circuit is called variable resistance.

Rheostat is a device used in electric circuit to change the resistance and hence current in circuit.

A conductor or material which offers low resistance to the flow of electrons or electric current in an electric circuit is called as good conductor.

A conductor or material which offers higher resistance to the flow of electrons or electric current in an electric circuit is called as bad conductor.

A material which offers very high resistance to the flow of electrons or electric current in an electric circuit is called as insulator.