# 💡Physics

Applicable for A-Level, IB, DSE, AP-Level Exams

# Electricity

## Current Voltage and Resistance

In electricity, there are three fundamental principals you need to grasp: current, voltage and resistance. Ohm's Law states that as long as resistance is kept constant, current and voltage is proportional. The fundamental definitions of V, I and R is crucial to learn in order to grasp the rest of the electricity chapter.

• Current is rate of flow of charge. This is expressed as charge over time.
• Voltage/Potential Difference between two points is work done per unit charge.
• Resistance is the amount of current you get for a particular potential difference. (Ohm's Law Reaaranged)

## I-V Characteristics

I-V Graphs is all about showing the relationship between potential difference and current. If a conductor obeys Ohm's Law, current is proportional to voltage and the graph will be a straight line through the origin. Non-ohmic conductors like the filament lamp has its curve flatten out due to electrical energy turning into heat energy and causing the metal to heat up - more vibrations cause electrons to move through the component more difficultly.

## Resistance and Resistivity

Resistance is voltage per unit current. Resistivity is porportional to resistivity. Resistivity is a measure of how much a particular material resists current flow.

## Power and Electrical Energy

Power is defined as the amount of enegry per unit time.