OHMS LAW

Question 1

1. State Ohms law

Answer 1

At constant temperature and pressure , the amount of current flowing through a conductor is directly proportional to the potential difference applied across its ends.

Question 2

2. What are ohmic and non ohmic conductors?

Answer 2

Ohmic-obeys ohms law
Non ohmic - doesn’t obey ohms law

Question 3

3. What are linear and non linear devices?

Answer 3

Linear- Which obey ohms law
Non linear-doesn’t obey ohms law.
i.e. for ohmic conductors V - I graph is a straight slope.

Question 4

4. Give examples for ohmic and non ohmic devices.

Answer 4

Examples for ohmic devices – Rheostat, carbon resistors
Examples for non ohmic devices – diodes, transistors

Question 5

5. Define resistance – resistivity (specific resistance) – conductance – conductivity (All SI units)

Answer 5

Resistance-Resistance is a substance’s opposition to the flow of electric current. R=rhol/A
SI unit-ohm
resistivity= RA/l
SI unit- ohm m
conductance=1/R
SI unit-ohm-1/mho / s
conductivity=1/rho
SI unit - ohm-1 m-1 / mho m-1/ sm-1

Question 6

6. Name the 4 factors depend on resistance of a wire?

Answer 6

Length, Area of cross section, nature of material, temperature

Question 7

7.Name the 2 factors depend on specific resistance ( resistivity)of a wire?

Answer 7

Nature of material, temperature

Question 8

8. Which material is preferred as standard resistance ?

Answer 8

Platinum (less corrosion)

Question 9

9. Best conductor

Answer 9

Silver ( lowest resistivity value)

Question 10

10. Best insulator

Answer 10

Diamond ( highest forbidden energy gap value)

Question 11

11. What is the nature of V – I graph in ohms law?

Answer 11

slope

Question 12

14. VA-1 is ?

Answer 12

Ohm

Question 13

15. What do you meant by temperature coefficient of resistance?

Answer 13

It indicates the variation of resistance in each substance according to variation in temperature .
ą=R2-R1/R1[t2-t1]
SI unit- K^-1
ą is -ve for insulators ,semi conductors and its +ve for conductors and alloys.