The SI unit of electric current is Ampere (symbol: A), named after the French physicist André-Marie Ampère. One Ampere is defined as one Coulomb of charge flowing past a point per second. Electric current (I) is the rate of flow of electric charge. The Ampere is one of the seven base SI units.
SI unit of electric current = Ampere (A).
Named after André-Marie Ampère, French physicist.
1 Ampere = 1 Coulomb per second (1 C/s).
Formula: I = Q/t (Current = Charge ÷ Time).
Ampere is one of the 7 base SI units.
Ohm's Law: V = IR → Current I = V/R.
SI Unit: Ampere (A) Symbol: A Named after: André-Marie Ampère (French physicist, 1775–1836)
Definition of Ampere: • Old definition: 1 Ampere is that constant current which, when maintained in two straight parallel conductors of infinite length placed 1 metre apart in vacuum, produces a force of 2 × 10⁻⁷ N per metre between them. • New definition (2019 SI revision): 1 Ampere is defined by fixing the value of the elementary charge e = 1.602176634 × 10⁻¹⁹ Coulombs exactly.
Formula: • I = Q / t – I = electric current (Ampere, A) – Q = electric charge (Coulomb, C) – t = time (seconds, s) • 1 Ampere = 1 Coulomb per second = 1 C/s
Ohm's Law: • V = I × R – V = Voltage (Volt, V) – I = Current (Ampere, A) – R = Resistance (Ohm, Ω) • So: I = V/R
Seven Base SI Units:
| Quantity | Unit | Symbol |
|---|---|---|
| Length | Metre | m |
| Mass | Kilogram | kg |
| Time | Second | s |
| Electric Current | Ampere | A |
| Temperature | Kelvin | K |
| Amount of Substance | Mole | mol |
| Luminous Intensity | Candela | cd |
Smaller and Larger Units:
| Unit | Value |
|---|---|
| Milliampere (mA) | 10⁻³ A |
| Microampere (µA) | 10⁻⁶ A |
| Kiloampere (kA) | 10³ A |
NCERT Reference: • Class 10 Physics Chapter 12 — Electricity • Class 12 Physics Chapter 3 — Current Electricity
The SI unit of electric current is Ampere (A), named after French physicist André-Marie Ampère. 1 Ampere = 1 Coulomb of charge flowing per second (I = Q/t). Ampere is one of the 7 base SI units. By Ohm's Law: V = IR, so current I = V/R. Smaller units include milliampere (mA = 10⁻³ A) and microampere (µA = 10⁻⁶ A).
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