IGCSE Physics: Electricity and Static Electricity

Comprehensive question and answer study flashcards for IGCSE Physics topics covering current, voltage, resistance, safety, energy, circuits, and static electricity.

What are the standard units and symbols for current, charge, and resistance?

Current is measured in amperes ($A$), charge in coulombs ($C$), and resistance in ohms ($\Omega$).

How does double insulation protect a user from electric shock without an earth wire?

Double insulation provides two layers of insulating material between the user and live electrical parts, eliminating the need for an earth wire.

How do an earth wire and a fuse work together to ensure electrical safety?

The earth wire provides a low-resistance path to ground if a metal case becomes live, causing a large current that melts the thin fuse wire and breaks the circuit.

What occurs at the microscopic level when current flows through a resistor to produce heat?

Electrons collide with particles in the material and transfer electrical energy into thermal energy.

How is electrical power defined, and what equation relates power, current, and voltage?

Power is the rate of energy transfer measured in watts ($W$), given by the equation $P = I \times V$.

What is the power transferred by an appliance connected to a $230\,V$ supply with a current of $5\,A$?

The power is $1150\,W$, calculated using $P = 5\,A \times 230\,V = 1150\,W$.

What is the key difference between direct current (DC) and alternating current (AC)?

Direct current (DC) flows in one direction only, whereas alternating current (AC) repeatedly reverses direction.

Why is domestic lighting connected in parallel rather than in series?

Parallel circuits allow lamps to operate independently so that if one breaks, others continue working, and each lamp receives the full supply voltage.

How does the current-voltage graph of a metal filament lamp differ from that of a fixed resistor at constant temperature?

A fixed resistor produces a straight line through the origin, whereas a filament lamp produces a curved graph because its resistance increases as the filament gets hotter.

How does a diode control the direction of current flow in a circuit?

A diode allows current to flow mainly in one direction once forward voltage is reached, but offers very high resistance in reverse.

How does light intensity affect the resistance of a Light-Dependent Resistor (LDR)?

Increasing light intensity causes lower resistance, while darker conditions cause higher resistance.

How is electric current defined in terms of charge flow, and what is its unit equivalent?

Current is the rate at which charge flows past a point ($I = \frac{Q}{t}$), where $1\,A = 1\,C/s$.

What is the movement direction of electrons in a metal conductor compared to conventional current?

Negatively charged electrons move from negative to positive, while conventional current is defined from positive to negative.

What rule applies to electric current at a circuit junction?

Current is conserved at a junction, meaning total current entering equals total current leaving.

How do total resistance and voltage behave across components in a series circuit?

Total resistance adds up ($R_{\text{total}} = R_1 + R_2$), and supply voltage is shared ($V_{\text{total}} = V_1 + V_2$), with larger resistances receiving a larger share.

How is voltage defined in terms of energy and charge, and what is its unit equivalent?

Voltage is energy transferred per unit charge passed ($V = \frac{E}{Q}$), where $1\,V = 1\,J/C$.

Why do metals conduct electricity while materials like plastic act as insulators?

Metals contain free electrons that can move through the material, whereas insulators do not allow charge to move easily.

Which subatomic particles are transferred during charging by friction, and how do they determine overall charge?

Only electrons are transferred; gaining electrons creates a negative charge, while losing electrons creates a positive charge.

Why is static electricity hazardous near fuel aircraft or tankers, and how is it mitigated?

Friction from movement causes static charge build-up, which can suddenly discharge as a spark and ignite fuel vapour; earthing or grounding safely dissipates this charge.

How is static electricity utilized in the function of a photocopier?

A charged surface creates a pattern corresponding to the document, attracting oppositely charged toner particles which are transferred to paper and fixed with heat.