Advertisements
Advertisements
Question
What length of copper wire of resistivity 1.7 × 10-8 Ω m and radius 1 mm is required so that its resistance is 2Ω?
Advertisements
Solution
Resistance (R) = 2 ohm
Resistivity (ρ) = 1.7 × 10-8 ohm metre
Radius (r) = 1 mm = 10-3 m
Length (l) = ?
`R=ρ l/A`
`ρ=l/(pir^2)`
Substituting the values in the formula above we get,
`2 = 1.7xx10^-8l/(pi(10^-3)^2)`
`2 = 1.7xx10^-8l/(3.14xx(10^-3)^2)`
`2=(1.7xx10^-2xxl)/3.14`
`2 =(1.7xxl)/314`
⇒ l = `(314xx2)/1.7`
⇒ l = 369.4 m
Hence, the length of the copper wire = 369.4 m.
RELATED QUESTIONS
The resistors R1, R2, R3 and R4 in the figure given below are all equal in value.
What would you expect the voltmeter A, B and C to read assuming that the connecting wires in the circuit have negligible resistance?
In a conductor 6.25 × `10^16` electrons flow from its end A to B in 2 s. Find the current flowing through the conductor (e = 1.6 × `10^-19` C)
How would you connect two resistors in series? Draw a diagram. Calculate the total equivalent resistance.
- Name and state the law which relates the potential difference and current in a conductor.
- What is the necessary condition for a conductor to obey the law named above in part (a) ?
Rewrite the following statement by selecting the correct option.
The S.I. unit of resistance is __________.
What are ohmic conductors? Give one exmaple. Draw a graph showing the current-voltage relationship for an ohmic conductor.
What are non-ohmic conductors? Give one exmaple. Draw a current-voltage graph for a non-ohmic conductor.
The resistance of a nichrome wire at 0°C is 10Ω. If its temperature coefficient of resistivity of nichrome is 0.004/ °C, find its resistance of the wire at boiling point of water. Comment on the result.
Ohm's law deals with the relationship between ______
State Ohm's Law. Represent it mathematically.
