📖 Glossary

Alkaline Cell (AA Battery)

A primary (non-rechargeable) battery that generates power through the reaction between Zinc and Manganese Dioxide. It uses an alkaline electrolyte (Potassium Hydroxide) and has a nominal voltage of 1.5V.

Anode

The electrode where oxidation occurs (the loss of electrons). In a discharging battery, the anode is the negative terminal.

Back-EMF (Counter Electromotive Force)

A voltage generated by a spinning motor that opposes the supply voltage. It increases with motor speed and limits current flow at high speeds.

Capacity (mAh)

A measure of the total electrical charge a battery can deliver. Expressed in Milliamp-hours (mAh), it can be converted to Coulombs (C) by multiplying by 3.6.

Formula: Q (Coulombs) = mAh × 3.6

Cathode

The electrode where reduction occurs (the gain of electrons). In a discharging battery, the cathode is the positive terminal.

Coulomb (C)

The SI unit of electric charge. One coulomb equals the charge of approximately 6.24 × 10¹⁸ electrons. 1 ampere-hour (Ah) = 3600 C.

Current (I)

The rate of flow of electric charge, measured in Amperes (A). I = Q/t (charge per unit time).

DC Motor

A device that converts direct current (DC) electrical energy into mechanical rotation. It works by passing current through a coil within a magnetic field, creating a force that turns the shaft.

Discharge Curve

A graph showing how battery voltage changes over time during discharge. Alkaline batteries show gradual voltage decline; NiMH batteries maintain voltage longer before dropping sharply.

Electrochemistry

The branch of chemistry dealing with the relationship between electrical and chemical changes. Batteries are electrochemical devices that convert chemical energy to electrical energy.

Electrode

A conductor through which electric current enters or leaves a device. In a battery, there are two electrodes: the anode (negative terminal during discharge) and the cathode (positive terminal during discharge).

Faraday Constant (F)

The charge of one mole of electrons: F = 96,485 C/mol. Used to calculate total charge from moles of electrons: Q = n × F.

Internal Resistance

The natural resistance within a battery. As current flows, this resistance causes a voltage sag, which is a drop in the voltage available to the device.

Formula: V_loaded = V_open - I × R_internal
but can be rearranged to: R_internal = (V_open - V_loaded)/I

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction, determining the maximum amount of product that can be formed.

Magnetic Field (B)

A region around a magnet or current-carrying conductor where magnetic forces can be detected. Measured in Tesla (T) or milliTesla (mT).

Molar Mass (M)

The mass of one mole of a substance, expressed in g/mol. Used to convert between mass and moles: n = m/M.

Examples - Zn: 65.38 g/mol; MnO₂: 86.94 g/mol

Mole (mol)

The SI unit for amount of substance. One mole contains exactly 6.022 × 10²³ particles (Avogadro's number).

NiMH (Nickel-Metal Hydride)

A rechargeable battery type using nickel oxyhydroxide and a hydrogen-absorbing alloy. Nominal voltage: 1.2V. Lower internal resistance than alkaline.

Oxidation

Loss of electrons. In an alkaline battery, zinc is oxidized: Zn → Zn²⁺ + 2e⁻.
You can remember "OIL", Oxidation Is Loss (of electrons).

Magnetic Permeability (μ)

A measure of how easily a material supports the formation of a magnetic field. Using high-permeability materials, like an iron core, significantly strengthens a magnetic field.

(permeability of free space) - μ₀ = 4π × 10⁻⁷ T×m/A

Redox Reaction

A reaction involving both reduction and oxidation. One species loses electrons (oxidized) while another gains them (reduced). All battery reactions are redox reactions.
You can use the mnemonic "OIL RIG" to remember that Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons).

Reduction

Gain of electrons. In an alkaline battery, MnO₂ is reduced.
Remember: "RIG", Reduction Is Gain (of electrons).

Right-Hand Rule

A visual technique for determining the direction of a magnetic field around a current-carrying wire (also is used for determining direction, force direction, and current direction in other scenarios). Point your thumb in the direction of conventional current flow (positive to negative), and your fingers will curl in the direction of the magnetic field lines that wrap around the wire.

Solenoid

A coil of wire that produces a magnetic field when current flows through it. The field inside is approximately uniform and proportional to current and number of turns.

Formula for Magnetic Field Strength: B = μ₀ × μᵣ × N × I / L

Stoichiometry

The branch of chemistry that calculates the quantitative relationships between reactants and products. It allows us to predict how much battery material is needed to produce a specific amount of electricity.

Torque (τ)

A rotational force that causes an object to spin. In a DC motor, torque is produced when the magnetic field exerts a force on the current-carrying armature coil. The motor's torque determines how much rotational "push" it can deliver to the wheels.

Formula: τ = F × r (force times radius)

Armature

The rotating part of an electric motor that carries the current-carrying coils. When current flows through the armature windings, it creates a magnetic field that interacts with the permanent magnets, causing the armature to spin and produce mechanical rotation.

Voltage (V)

Electric potential difference, measured in Volts. It represents the "push" that drives current through a circuit. Energy per unit charge: V = E/Q.
Formula (Ohm's Law): V = I × R

Voltage Sag

The drop in battery voltage when current is drawn, caused by internal resistance. Higher current = more sag.

Watt (W)

The SI unit of power, measuring the rate at which energy is used or transferred. One watt = one joule per second. Formulas: (total power) P = V × I, (power loss/dissipation) P = I²R

Watt-hour (Wh)

A unit of energy equal to one watt of power sustained for one hour. 1 Wh = 3600 J. Useful for comparing battery capacities.