JEE · Physics · Current Electricity doubts

What does “Ohm's law” actually mean in Current Electricity, and why does it matter for JEE?

for many conductors V = IR at constant temperature.

I keep getting “Ohm's law” questions wrong in Current Electricity. What's the trap?

assuming every component is ohmic (a diode or bulb filament is not).

What does “Resistance and resistivity” actually mean in Current Electricity, and why does it matter for JEE?

R = ρL/A: resistance grows with length and shrinks with cross-section; resistivity ρ is the material's own property.

I keep getting “Resistance and resistivity” questions wrong in Current Electricity. What's the trap?

confusing resistance (depends on shape) with resistivity (depends only on material and temperature).

What does “Series and parallel resistors” actually mean in Current Electricity, and why does it matter for JEE?

in series the current is the same and resistances add; in parallel the voltage is the same and 1/R values add.

I keep getting “Series and parallel resistors” questions wrong in Current Electricity. What's the trap?

adding parallel resistances directly instead of their reciprocals.

What does “EMF and terminal voltage” actually mean in Current Electricity, and why does it matter for JEE?

EMF is the battery's full push; terminal voltage is what's left after the internal resistance drops some of it.

I keep getting “EMF and terminal voltage” questions wrong in Current Electricity. What's the trap?

assuming terminal voltage equals EMF even when current flows.

What is the difference between series connection and parallel connection?

In series components share the current and split the voltage; in parallel they share the voltage and split the current.

What is the difference between EMF and terminal voltage?

EMF is the source's total energy per charge; terminal voltage is the usable voltage after internal-resistance losses.

What is the difference between resistance and resistivity?

Resistance (Ω) depends on the object's size and shape; resistivity (Ω·m) is an intrinsic material property.

When do I use V = IR in Current Electricity, and what does it mean?

Ohm's law relating voltage, current and resistance.

When do I use R = ρL/A in Current Electricity, and what does it mean?

resistance from resistivity, length and area.

When do I use P = VI = I²R = V²/R in Current Electricity, and what does it mean?

electrical power dissipated.