Quick Review Flashcards - Click to flip and test your knowledge!
Question
What are the two types of subatomic particles found in the nucleus of an atom?
Answer
Protons and neutrons.
Question
The electrons in the orbits closest to the nucleus that are strongly attracted to it are known as ____ electrons.
Answer
Bound
Question
What is the name for the electrons in the outermost orbit that can be easily detached from an atom?
Answer
Free electrons.
Question
Which particles act as the charge carriers responsible for electric conduction in metals?
Answer
Free electrons.
Question
What happens to the charge of an atom if it loses one or more electrons?
Answer
It becomes positively charged.
Question
Term: Conductors
Answer
Definition: Substances like silver, copper, and aluminium that have a large number of free electrons and allow electricity to flow through them.
Question
How does the electrical conductivity of a semiconductor change with a rise in temperature?
Answer
It increases.
Question
Substances like wood, glass, and rubber that have almost negligible free electrons are classified as ____.
Answer
Insulators
Question
What is the term for the state where some materials allow electric current to flow without any resistance when cooled below a critical temperature?
Answer
Superconductivity
Question
The S.I. unit of electric charge is the ____.
Answer
Coulomb ($C$)
Question
Formula: Quantum nature of charge
Answer
$q = \pm ne$ (where $n$ is an integer and $e$ is the elementary charge).
Question
What is the magnitude of the charge on a single electron ($e$)?
Answer
$1.6 \times 10^{-19}\text{ C}$
Question
How many nanocoulombs ($nC$) are in $1\text{ Coulomb}$?
Answer
$10^{9}\text{ nC}$ (or $1\text{ nC} = 10^{-9}\text{ C}$).
Question
When two charged conductors are joined by a wire, electrons flow from the conductor with a ____ concentration of electrons to the one with a lower concentration.
Answer
Higher
Question
What determines the magnitude of electric current ($I$) according to its definition?
Answer
The rate of flow of charge ($I = \frac{Q}{t}$).
Question
In an electrolyte, current flows due to the movement of which two types of particles?
Answer
Positive ions and negative ions.
Question
Is electric current a scalar or a vector quantity?
Answer
Scalar quantity.
Question
By convention, in which direction is electric current said to flow?
Answer
From positive to negative (the direction of flow of positive charge).
Question
Electronic current flows in the ____ direction to conventional current.
Answer
Opposite
Question
The S.I. unit of electric current is the ____.
Answer
Ampere ($A$)
Question
How many electrons must pass through a cross-section in one second to constitute a current of $1\text{ Ampere}$?
Answer
$6.25 \times 10^{18}$ electrons.
Question
A conductor having an excess of electrons is said to be at a ____ potential.
Answer
Negative (or lower)
Question
A conductor having a deficit of electrons is said to be at a ____ potential.
Answer
Positive (or higher)
Question
Formula: Potential Difference ($V$)
Answer
$V = \frac{W}{q}$ (where $W$ is work done and $q$ is charge).
Question
What is the S.I. unit of potential difference?
Answer
Volt ($V$)
Question
Define $1\text{ Volt}$ in terms of work and charge.
Answer
The potential difference between two points when $1\text{ Joule}$ of work is done in transferring $1\text{ Coulomb}$ of charge.
Question
The obstruction offered to the flow of current by a conductor is called its ____.
Answer
Electrical resistance
Question
What is the primary cause of electrical resistance in a metallic wire?
Answer
Collisions of moving electrons with fixed positive ions and other electrons.
Question
Formula: Ohm's Law
Answer
$V = IR$ (where $R$ is resistance).
Question
What is the S.I. unit of electrical resistance?
Answer
Ohm ($\Omega$)
Question
How does the length of a wire affect its electrical resistance?
Answer
Resistance is directly proportional to the length ($R \propto \text{length}$).
Question
How does the area of cross-section of a wire affect its resistance?
Answer
Resistance is inversely proportional to the area of cross-section ($R \propto \frac{1}{A}$).
Question
Why does the resistance of a metallic wire increase as its temperature increases?
Answer
The metal ions vibrate more violently, leading to an increased number of collisions for moving electrons.
Question
In a dry cell, what component acts as the positive terminal?
Answer
The brass cap (at the centre).
Question
In a dry cell, what component acts as the negative terminal?
Answer
The zinc case (base).
Question
What is the main functional difference between a primary cell and a secondary cell?
Answer
Primary cells involve irreversible chemical reactions and cannot be recharged, while secondary cells are rechargeable.
Question
Which type of cell (primary or secondary) typically has a lower internal resistance?
Answer
Secondary cell.
Question
Give an example of a secondary cell.
Answer
Lead (or acid) accumulator (or Ni-Fe, Li-ion batteries).
Question
Concept: Battery
Answer
Definition: A combination of two or more cells joined in series (cathode of one to anode of another).
Question
What is the purpose of an electric key (or switch) in a circuit?
Answer
To put the current on or off by completing or breaking the circuit.
Question
Term: Rheostat
Answer
Definition: A device used to vary the resistance in a circuit continuously to adjust the magnitude of current.
Question
Which instrument is used to measure the magnitude of current and must be connected in series?
Answer
Ammeter
Question
Which instrument is used to measure potential difference and must be connected in parallel?
Answer
Voltmeter
Question
Why must an ammeter have a very low resistance?
Answer
To ensure it does not significantly alter the current flowing in the circuit it is measuring.
Question
Why must a voltmeter have a very high resistance?
Answer
To ensure it does not draw an appreciable current from the circuit.
Question
Which instrument is used to detect the presence of a very weak current or to know its direction?
Answer
Galvanometer
Question
Term: Load
Answer
Definition: An appliance (such as a bulb or heater) connected in a circuit that uses electrical energy.
Question
What happens to the total current in a circuit if you increase the resistance while keeping the potential difference constant?
Answer
The current decreases.
Question
What condition must be met for a circuit to be considered 'closed'?
Answer
The path for the current must be complete and made of conducting materials.
Question
Why are connecting wires in a circuit typically made of copper?
Answer
Copper is highly conducting and has negligible resistance.
Question
How is a d.c. source (cell) represented symbolically?
Answer
By two parallel vertical lines of unequal lengths, where the longer line is '+' and the shorter is '-'.
Question
What energy transformation occurs in a cell when it is providing current?
Answer
Chemical energy changes into electrical energy.
Question
If a body has a deficit of electrons, what is the nature of its charge?
Answer
Positive
Question
The rate of flow of electrons in a specific direction is known as ____ current.
Answer
Electronic
Question
How does a thinner wire's resistance compare to a thicker wire of the same length and material?
Answer
The thinner wire offers more resistance.
Question
In symbols, what does '$Rh$' stand for?
Answer
Variable resistance (or a rheostat).
Question
What is the equivalent value of $1\text{ microampere (}\mu A\text{)}$ in Amperes?
Answer
$10^{-6}\text{ A}$