Physics Questions

Bicycle is a compound machine in the above given options. A compound machine is a machine that is formed by two or more simple machines.

Resistivity :

Resistivity is a measure of the resistance to the flow of electrons. 

Conductivity :

Conductivity is just the inverse of resistivity, σ = 1/ρ, where σ is conductivity and ρ is resistivity.

Example:

Think of a pipe and water, the bigger the pipe, the easier water can flow and thus the lower the resistance. 

Electrical discharge machining (EDM), also known as spark machining, spark eroding, burning, die sinking, wire burning or wire erosion, is a manufacturing process whereby a desired shape is obtained by using electrical discharges.

From the given circuit,

The resistors R1 and R2 are in parallel connection and R3 is in series with R1 & R2

The equivalent resistance of R1 and R2 is

Req = (12 × 4)/(12 + 4) = 3 Ω.

Adding R3 in series with the pair gives

R = Req + 9

R = 3 + 9

R = 12 Ω.

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2% and is a brittle material.

Its usefulness derives from its relatively low melting temperature.

Violet colour has the highest energy. The higher the frequency, the faster the oscillations and thus the higher the energy. Therefore, the highest-frequency ultra-violet light or the lowest wavelength is violet.