1. Voltage (V) β Electrical Pressure
Volts (V)
Think of Voltage as water pressure in a high-elevation water tank. It is the electromotive force that pushes electrons through a conductor. Higher voltage creates greater pressure to move electric charges.
π‘ Analogy: A 9V battery has 6x more pushing force than a 1.5V AA cell.
2. Current (I) β Rate of Flow
Amperes (A / mA)
Current is the quantity of electrons actually passing through a cross-section of wire per second ($1\text{ Ampere} = 6.242 \times 10^{18}$ electrons/sec). This is what does physical workβlighting an LED, turning a motor, or creating heat.
3. Resistance (R) β Flow Obstruction
Ohms (Ξ©)
Resistance opposes the flow of electrons, analogous to a narrow constriction in a water pipe. Resistors drop voltage and limit current to protect sensitive components like LEDs from burnout.
Adjust the sliders below to witness live how changing Voltage or Resistance alters electron flow (Current) and Power dissipation.
CALCULATED CURRENT (I)
I = V / R
POWER CONSUMED (P)
P = V Γ I
β‘ Why LEDs Pop Without a Resistor
Standard 5mm LEDs have an internal forward resistance of roughly only $10\Omega$ to $15\Omega$.
If you connect a 9V battery directly to an LED without a current-limiting resistor:
I = 9V / 12Ξ© β 0.75 Amperes (750 mA)
Since LEDs are only rated for a maximum of 25mA to 35mA, 750mA is over 20 times the maximum rating! The microscopic semiconductor die instantly overheats, pops, and breaks the circuit.
β οΈ Short Circuit Hazard
A short circuit occurs when current finds a low-resistance return path directly back to the power supply without passing through a functional load. This causes extreme current spikes, sparking, and battery drain.