Physics (Part-ix) (Railway)

The SI unit of resistance is ohm, which is defined as a volt per ampere.

Ω = V/A

Given,

I₂ = 31₁

Using,

I₁A₁ = I₂A₂

I₁A₁ = 31₁A₂

A₂ = A₁/3

R₂ = ρ l₂/A₂ =  ρ 3l₁/A₁/3  = 9ρ l₁/A₁

R₂ = = 9R

Fleming's right-hand rule shows the direction of the induced current when a conductor moves in a magnetic field.

• It can be used to determine the direction of current in a generator's winding.

• The thumb is pointed in the direction of motion of the conductor.

R = p L/A

⇒ R = p L/πr²

P = Rπr²/L

⇒ P = 10 * 3.14 * (0.227)²/1000

= = 1.54 × 1.0-⁶Ω -m

When two parallel wires carry current in the same direction, they exert equal and opposite attractive forces on each other and repel each other when the current is in opposite direction.

• This can be verified using Fleming's left-hand rule.

• The directions of the magnetic fieldsproduced by the two conductors will be opposite to each other.

The rate of work done is called power. Rate of electric work done is called electric power.

• Electric power is the rate at which electric energy is dissipated or consumed in an electric circuit.

Fuse (Made of Tin (Sn) and lead (Pb) is a safety device consisting of a wire that melts and breaks an electric circuit if the current exceeds a safe level.

• So, Fuse wire should have high resistance and low melting point.

• Low melting point lets it break the circuit when high current passes through it. It melts. thus, saving electric devices from damage.

f = - 12cm

v = - 8cm

u=?

1/v - 1/u = 1/f ;1/u = 1/v - 1/f

= 1/- 8 - 1/- 12 = - 1/8 + 1/12

1/u = - 3 + 2/24 ; 1/u = - 1/24

u = - 24cm

The center of the spherical mirror that forms the curved mirror is called the center of curvature.

• The center of the aperture of the curved mirror is called the pole of the curved mirror.

• The imaginary line that joins the pole to the curved mirror to the center of curvature of the curved mirror is called the principal axis.

Resistance of a conductor Is a property by virtue of which It opposes the flow of electric current in it.

• It is directly proportional to length and inversely proportional to area of cross-section of the substance.