Advertisements
Advertisements
प्रश्न
Obtain the macroscopic form of Ohm’s law from its microscopic form and discuss its limitation.
Advertisements
उत्तर
- Consider a segment of wire of length l and area of cross-section A
- Electric field is created when a potential difference V is applied
- If ‘E’ is uniform, then, V = El
- Current density, J = σ E = σ`"V"/l`
Since J = `"I"/"A"`
`"I"/"A" = sigma "V"/l`
Rearranging the above equation, Current through the conductor
Current through the conductor
V = `"I"(l/(sigma"A"))`
Where `(l/(sigma"A"))` → resistance of conductor (R)
∴ R `alpha (l/(sigma"A"))`
∴ The macroscopic form of Ohm's law is
V = IR ...[V α I]
Limitations:
There are certain materials and devices where the proportionality of V and I does not hold good.
APPEARS IN
संबंधित प्रश्न
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
The relationship between the potential difference and the current in a conductor is stated in the form of a law.
1) Name the law.
2) What does the slope of V-I graph for a conductor represent?
3) Name the material used for making the connecting wire.
What is an ohmic resistor? Give one example of an ohmic resistor. Draw a graph to show its current voltage relationship. How is the resistance of the resistor determined from this graph?
How does an increase in the temperature affect the specific resistance of a :
(i) Metal and
(ii) Semiconductor ?
Fig. represents the circuit used for the verification of Ohm's law. Label the parts from A to F. state the function of each.
What are non-ohmic conductors? Give one exmaple. Draw a current-voltage graph for a non-ohmic conductor.
Choose the correct alternative.
Which of the following is an ohmic conductor?
Ohm’s law states the relationship between power and voltage.
Assertion: The statement of Ohm’s law is K = IR.
Reason: V = IR is the equation which defines resistance.
