Physics

Conventional Current Flow

Assumes positive charge flows from the positive terminal (+) to the negative terminal (-) through the external circuit.

Electron Flow

The actual movement of electrons from the negative terminal (-) to the positive terminal (+).

Electric Circuit

A complete closed pathway that allows electric current to flow.

Electric Charge (Q)

The quantity of electricity transferred through a circuit; measured in Coulombs (C).

Electric Current (I)

The rate at which electric charge flows through a circuit (I = Q/t); measured in Amperes (A).

Voltage / Potential Difference (V)

The energy transferred per unit of charge (V = E/Q); measured in Volts (V).

Electrical Resistance (R)

The opposition to the flow of electric current; measured in Ohms (Ω).

Electrical Energy (E)

The amount of energy transferred by an electrical component (E = VIt or E = Pt); measured in Joules (J).

Electrical Power (P)

The rate at which electrical energy is transferred (P = VI); measured in Watts (W).

Electrical Potential Energy

Stored energy an electron possesses based on its distance and charge relative to another charged particle.

Ammeter

Instrument used to measure electric current; connected in series and has very low resistance.

Voltmeter

Instrument used to measure potential difference; connected in parallel across a component and has very high resistance.

Ohm's Law

Describes the relationship between voltage current and resistance: V = IR.

Electrical Power Formulas

P = VI, P = I^2 * R, and P = V^2 / R.

Series Circuit Rules

Single path: Current is the same throughout, Voltage is shared across components, Resistance adds up (R_total = R1 + R2).

Parallel Circuit Rules

Multiple paths: Current splits across branches, Voltage is the same across all branches, Resistance decreases (1/R_total = 1/R1 + 1/R2).

Distance-Time Graph Gradient

Gradient equals velocity (v = Δs/Δt); straight diagonal line = constant velocity, horizontal line = stationary.

Velocity-Time Graph Gradient

Gradient equals acceleration (a = Δv/Δt).

Velocity-Time Graph Area

Area under the graph equals displacement (s).

Acceleration-Time Graph Area

Area under the graph equals the change in velocity (Δv).

SUVAT Variables

s = displacement (m), u = initial velocity (m/s), v = final velocity (m/s), a = acceleration (m/s²), t = time (s).

SUVAT: Missing Displacement (s)

v = u + at

SUVAT: Missing Final Velocity (v)

s = ut + (1/2)at^2

SUVAT: Missing Acceleration (a)

s = ((u + v) / 2) * t

SUVAT: Missing Time (t)

v^2 = u^2 + 2as

SUVAT: Missing Initial Velocity (u)

s = vt - (1/2)at^2

SUVAT Applicability Rule

SUVAT equations can only be used when acceleration is constant.

Net Force (F_net)

The vector sum of all forces acting on an object; F_net = 0 means balanced forces (no acceleration), F_net ≠ 0 causes acceleration.

Newton's Second Law

F_net = ma (Net Force = mass × acceleration).

Perpendicular Forces Formula

Resultant force F_R = √(F_x^2 + F_y^2).

Horizontal Vector Component (Fx)

Fx = F * cos(θ) (when angle θ is measured from the horizontal).

Vertical Vector Component (Fy)

Fy = F * sin(θ) (when angle θ is measured from the horizontal).

Angle of Resultant Force

θ = tan⁻¹(Fy / Fx).

Weight / Gravitational Force (Fg)

Fg = mg (mass × gravitational field strength).