1 Electrical Quantities and Ohm’s Law Free Online FlashCards

What is electric charge, and what is its SI unit?

Electric charge is a property of matter, measured in coulombs (C).

What is electric current, and how is it calculated?

Current is the rate at which charge passes a point: $I = \frac{Q}{t}$. It is measured in amperes $A$, where $1\,\text{A} = 1\,\text{C/s}$.

What does voltage measure, and what is its unit?

Voltage is energy transferred per unit charge: $V = \frac{E}{Q}$. It is measured in volts $V$, where $1\,\text{V} = 1\,\text{J/C}$.

What does resistance describe, and what is its unit?

Resistance describes how strongly a component opposes current. It is measured in ohms $Ω$, with $1\,\Omega = 1\,\text{V/A}$.

What is Ohm’s law, and which components does it describe?

For ohmic components under the conditions considered, voltage, current, and resistance follow $V = IR$. Not every component has this proportional relationship.

What is electrical power, and how can it be calculated?

Electrical power is the rate of energy transfer. For a circuit element, $P = VI$; power is measured in watts $W$, where $1\,\text{W} = 1\,\text{J/s}$.

How do you calculate energy transferred over time?

Energy transferred over a time interval is power multiplied by time: $E = Pt$. Energy is measured in joules $J$.

What is the magnitude of an electron’s charge?

The magnitude of an electron’s charge is approximately $1.602 \times 10^{-19}\,\text{C}$.

How can charge be calculated from current and time?

Rearranging $I = \frac{Q}{t}$ gives $Q = It$.

Between what is voltage measured?

Voltage is measured between two points.

How does current change when voltage or resistance increases?

With resistance fixed, increasing voltage increases current. With voltage fixed, increasing resistance decreases current.

What current flows through a $6\,\Omega$ resistor across $12\,\text{V}$?

Using $I = \frac{V}{R}$, the current is $\frac{12\,\text{V}}{6\,\Omega} = 2\,\text{A}$.