Question 1

What is Ohm's law?

Accepted Answer

Ohm's law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with resistance (R) as the constant of proportionality: V = I × R. It was formulated by German physicist Georg Simon Ohm in 1827 and is the foundational relationship in circuit analysis.

Question 2

How do I calculate resistance from voltage and current?

Accepted Answer

Use the formula R = V / I. If you have 120 volts across a load drawing 5 amperes, the resistance is 120 / 5 = 24 ohms. Rearranging Ohm's law gives you the three primary forms: V = I × R, I = V / R, and R = V / I.

Question 3

What is the power formula in electronics?

Accepted Answer

The basic power formula is P = V × I (watts = volts × amperes). Combining with Ohm's law gives two additional forms: P = I² × R (power from current and resistance) and P = V² / R (power from voltage and resistance). All four quantities — V, I, R, and P — are related through these equations.

Question 4

How do you calculate voltage from power and resistance?

Accepted Answer

When power (P) and resistance (R) are known, voltage is calculated as V = √(P × R). For example, a 100 W load with 10 Ω resistance has a voltage of √(100 × 10) = √1000 ≈ 31.62 V. This formula comes from combining P = V²/R and solving for V.

Question 5

What units are used in Ohm's law?

Accepted Answer

Ohm's law uses SI units: Voltage in Volts (V), Current in Amperes (A), Resistance in Ohms (Ω), and Power in Watts (W). The relationships are dimensionally consistent: 1 V = 1 A × 1 Ω, and 1 W = 1 V × 1 A = 1 A² × 1 Ω = 1 V² / 1 Ω.