B.5 Current and circuits

Question 1

Electrical Conductors

Answer 1

Materials that allow electricity to flow easily due to the movement of electrons. Metals are common examples

Question 2

Electrical Insulators

Answer 2

Materials that do not allow electricity to flow easily. Examples include wood and rubber, which have fewer mobile charge carriers

Question 3

Electric Potential Difference (Voltage)

Answer 3

The work done per unit charge in moving a positive charge between two points. It is measured in volts (V).

Question 4

Electric Current

Answer 4

The rate of flow of charge, measured in amperes (A). Represents how much charge flows past a point per second

Question 5

Electromotive Force (emf)

Answer 5

The energy that a source of electrical energy transfers to each unit of charge. Measured in volts (V)

Question 6

Ohm’s Law

Answer 6

States that the current through a conductor between two points is directly proportional to the voltage across the two points. Represented as V = IR

Question 7

Resistance (R)

Answer 7

A measure of the difficulty encountered by current when flowing through a conductor. Calculated as R=V/I, measured in ohms (Ω)

Question 8

Resistivity (ρ)

Answer 8

A material’s intrinsic property indicating how strongly it resists current flow. Calculated as ρ=RA/L, measured in ohm meters (Ω⋅m)

Question 9

Ohmic vs. Non-Ohmic Conductors

Answer 9

Ohmic conductors have a constant resistance over a range of voltages, showing a linear V-I relationship. Non-ohmic conductors display a non-linear V-I relationship, with resistance varying with voltage

Question 10

Factors Affecting Resistance

Answer 10

The resistance of a conductor depends on its material (resistivity), length, and cross-sectional area. Longer wires and thinner wires have higher resistance

Question 11

Series Circuit

Answer 11

A circuit where components are connected in a single path. The current is the same through all components, but the voltage divides among them

Question 12

Parallel Circuit

Answer 12

A circuit where components are connected across common points or junctions, offering multiple paths for the current. Voltage is the same across each component

Question 13

Current in Series

Answer 13

In a series circuit, the current is the same through all components because there is only one path for electron flow

Question 14

Current in Parallel

Answer 14

In a parallel circuit, the total current is the sum of the currents through each parallel branch

Question 15

Voltage in Series and Parallel

Answer 15

In series circuits, voltages add up to the source voltage. In parallel circuits, all components share the same voltage

Question 16

Electromotive Force (emf)

Answer 16

The maximum potential difference between two electrodes of a cell; measures the energy provided per coulomb of charge.

Question 17

Internal Resistance (r)

Answer 17

The resistance within the battery or cell itself, which causes a decrease in the output voltage when a current flows.

Question 18

Total Voltage Equation for a Cell

Answer 18

Given by ϵ=I(R+r), where ϵ is the emf,
I the current, R the external resistance, and r the internal resistance

Question 19

Terminal Voltage (V)

Answer 19

The voltage measured across the terminals of a battery or cell, calculated as ϵ−Ir, where I is the current and r is the internal resistance

Question 20

Variable Resistors

Answer 20

Components that allow the resistance within a circuit to be adjusted. Used to control current flow without changing the circuit layout

Question 21

Power in Electrical Circuits

Answer 21

The rate at which electrical energy is transferred by an electric circuit. It is calculated as Power (P) = Voltage (V) × Current (I), measured in watts (W)

Question 22

The Law of Conservation of Energy in Circuits

Answer 22

States that energy cannot be created or destroyed in an isolated system. In electrical circuits, the total energy supplied by the source equals the energy converted into other forms

Question 23

Kirchhoff’s Voltage Law

Answer 23

In any closed loop in a circuit, the sum of all the voltages around the loop is equal to zero. This is due to the conservation of energy

Question 24

Kirchhoff’s Current Law

Answer 24

The total current entering a junction equals the total current leaving the junction. This law is based on the principle of conservation of charge

Question 25

The Principle of Superposition in Circuits

Answer 25

In a linear network with several independent sources, the voltage and current in any part of the network can be found by adding the voltages and currents from each source separately