Electricity & Magnetism
Electricity and magnetism are two aspects of the same fundamental force — electromagnetism — one of the four fundamental forces of nature.
Electric Charge & Current
Atoms contain positive protons and negative electrons. Like charges repel; opposite charges attract. Electric current (I) = flow of charge, measured in amperes (A).
Voltage & Resistance
Voltage (V) = electric potential difference, measured in volts (V). It's the "push" driving current.
Resistance (R) = opposition to current flow, measured in ohms (Ω).
Ohm's Law
V = IR (Voltage = Current × Resistance)
A circuit has 12V battery and 4Ω resistance.
I = V/R = 12/4 = 3 A
Series vs Parallel Circuits
Series: components in one loop. If one fails, all fail. Resistance adds: Rₜ = R₁ + R₂
Parallel: components in separate branches. One can fail without affecting others. Used in home wiring.
Magnetism
Moving charges create magnetic fields. Permanent magnets have north and south poles — opposites attract. Earth has a magnetic field that protects us from solar radiation. Electromagnets use coiled wire with current.
FAQ
Why do birds sit on power lines without being electrocuted? Current flows from high to low potential. Birds aren't connected to ground, so no current flows through them.
Quick Quiz
Test what you just learned. Choose the best answer for each question.