5. If a eire has resistance 200 Ω and the current through it is 0.5A,

1.	5. If a eire has resistance 200 Ω and the current through it is 0.5A, the p.d. across thewire must be ………….. a) 400V b) 200V c) 100V d) 50V
Answer» Given:- $\sf{<klux>RESISTANCE</klux> (R) = 200 \Omega}$ $\sf{Current (I) = 0.5 A}$ To find:- Potential DIFFERENCE across the wire. Solution:- According to Ohm's Law, $\sf{v = IR}$ $\sf{v = 0.5\times200}$ $\sf{v = 100 V}$ $\sf{\therefore The\:Potential\:Difference\:across\:the\:wire\:is\:100V}$ Important Informations:- v = Potential Difference across the conductor I = Current Flowing through the conductor R = Resistance across the conductor What is Resistance? Resistance is something which resists the FLOW of electrons through a conductor. Factors on which Resistance depends:- 1. LENGTH:- Resistance of a conductor is directly proportional to its length. The more the length the higher the resistance, i.e. if the length of a conductor is more, then the resistance across it will ALSO be more. $\sf{R\propto L \longrightarrow (i)}$ 2. Area of cross-section of the conductor:- The resistance is inversely proportional to the area of cross-section of a conductor. If the area of the conductor is more the the resistance across that conductor would be less. $\sf{R\propto\dfrac{1}{A}\longrightarrow (ii)}$ Combining Eq.(i) and (ii) $\sf{R\propto \dfrac{L}{A}}$ $\sf{\implies R = \rho\dfrac{l}{A} \:\:[Where \: \rho\:is\:constant]}$ $\sf{\rho\:pronounced\:as\:rho\:is\:called\:the\:resistivity\:of\:a\:conductor}$ 3. Material of the conductor:- Resistance also depends on the material of the conductor. A conductor with same area of cross-section and length but different material have different resistance. Material of a conductor is denoted by $\sf{\rho}$ . Hence, $\sf{\rho = \dfrac{RA}{L}}$ What is ohm's law? Ohm's law states that the potential difference across the conductor is directly proportional to current flowing through a conductor, where resistance of the conductor is constant. $\sf{Mathematically,\:\:\:\: V\propto I}$ $\sf{\implies V = IR\:\:\:[Where\:R\:is\:constant]}$ The SI unit of Resistance is $\sf{\Omega}$

5. If a eire has resistance 200 Ω and the current through it is 0.5A, the p.d. across thewire must be ………….. a) 400V b) 200V c) 100V d) 50V

Answer»

Given:-

$\sf{<klux>RESISTANCE</klux> (R) = 200 \Omega}$
$\sf{Current (I) = 0.5 A}$

To find:-

Potential DIFFERENCE across the wire.

Solution:-

According to Ohm's Law,

$\sf{v = IR}$

$\sf{v = 0.5\times200}$

$\sf{v = 100 V}$

$\sf{\therefore The\:Potential\:Difference\:across\:the\:wire\:is\:100V}$

Important Informations:-

v = Potential Difference across the conductor
I = Current Flowing through the conductor
R = Resistance across the conductor

What is Resistance?

Resistance is something which resists the FLOW of electrons through a conductor.

Factors on which Resistance depends:-

1. LENGTH:- Resistance of a conductor is directly proportional to its length. The more the length the higher the resistance, i.e. if the length of a conductor is more, then the resistance across it will ALSO be more.

$\sf{R\propto L \longrightarrow (i)}$

2. Area of cross-section of the conductor:- The resistance is inversely proportional to the area of cross-section of a conductor. If the area of the conductor is more the the resistance across that conductor would be less.

$\sf{R\propto\dfrac{1}{A}\longrightarrow (ii)}$

Combining Eq.(i) and (ii)

$\sf{R\propto \dfrac{L}{A}}$

$\sf{\implies R = \rho\dfrac{l}{A} \:\:[Where \: \rho\:is\:constant]}$

$\sf{\rho\:pronounced\:as\:rho\:is\:called\:the\:resistivity\:of\:a\:conductor}$

3. Material of the conductor:- Resistance also depends on the material of the conductor. A conductor with same area of cross-section and length but different material have different resistance.

Material of a conductor is denoted by $\sf{\rho}$ .

Hence,

$\sf{\rho = \dfrac{RA}{L}}$

What is ohm's law?

Ohm's law states that the potential difference across the conductor is directly proportional to current flowing through a conductor, where resistance of the conductor is constant.

$\sf{Mathematically,\:\:\:\: V\propto I}$

$\sf{\implies V = IR\:\:\:[Where\:R\:is\:constant]}$

The SI unit of Resistance is $\sf{\Omega}$