Charge and Current Quiz

Study Notes

Charge and Current

Electric current (I) measures the rate of flow of charge, defined as I = Q/t.
The SI unit for current is Amperes (A). Current is measured with an ammeter and always placed in series in a circuit.
Charge (Q) is a physical quantity that can be positive or negative, measured in coulombs (C).
1 coulomb equals the flow of charge in 1 second with 1 ampere of current, with SI base units of Coulombs (C).
Like charges repel; opposite charges attract. Charge values are quantized with a proton having +1 and an electron -1, representing multiples of the elementary charge, e = 1.6 x 10^-19 C.
Net charge for a particle is given by Q = ± ne, where n indicates the number of electrons gained or lost.
Increasing electrons yields a negative ion, while removing them results in a positive ion.

Charge Carriers

Electric current flows via different charge carriers based on the material; in metals, it is predominantly through electrons.
In metals, electrons move among a lattice of fixed positive ions, creating current when one side is negatively charged and the opposite positively charged.
Electrolytes are conducting liquids, often ionic solutions like saltwater (NaCl), allowing current to flow when electrodes are immersed, with cations attracted to the cathode and anions to the anode.

Conventional Current

Conventional current is defined as the flow of charge from the positive to the negative terminal, established prior to the discovery of electrons.
In metals, electrons move from negative to positive, opposite to the direction of conventional current flow.

Kirchhoff's First Law

Kirchhoff’s first law states that the sum of currents entering a point is equal to the sum exiting that point, reflecting conservation of charge.
Charge is a fundamental property that cannot be created or destroyed, ensuring its conservation in a circuit.

Mean Drift Velocity

Mean drift velocity (v) describes the average speed of electrons as they move through a metal, where they encounter random collisions with positive metal ions.
Number density (n) represents the number of free electrons per unit volume; metals have high number densities (~10^28 m^-3), while insulators have much lower values.
In materials with lower number densities, electrons must travel faster to carry the same current.
An additional formula for current can be derived relating charge, drift velocity, and number density.

Description

Test your knowledge on electric charge and current with this quiz. Explore concepts like the definition of current, the SI unit of charge, and the behavior of charge carriers in various materials. Challenge yourself and understand the fundamentals of electricity!