Test: Current Electricity - Class 10 MCQ

In a parallel circuit, the voltage across all resistors remains constant. This characteristic allows different paths for current to flow, which can be advantageous in circuit design for ensuring that components receive the same voltage.

Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant. This relationship is fundamental in understanding how electrical circuits operate.

Linear resistors or ohmic resistors obey Ohm's Law, meaning that the current through them is proportional to the voltage across them. This linear relationship is crucial for predictable circuit behavior.

When current is drawn from a cell, the terminal voltage is less than the electromotive force due to internal resistance within the cell. This difference is critical for understanding how effectively a cell can deliver power to a circuit.

The SI unit of electric current is the ampere (A), which is defined as the rate of flow of charge. One ampere corresponds to one coulomb of charge passing through a conductor per second. Understanding the unit of current is crucial for electrical calculations and circuit designs.

Nichrome is an ideal material for heating elements due to its high resistivity and ability to withstand high temperatures without degrading. This property ensures that it can efficiently convert electrical energy into heat.

Electrical resistance refers to the opposition to the flow of electric current within a conductor. It is an important factor in determining how much current can flow for a given voltage, influencing circuit design and efficiency.

Potential difference is a scalar quantity, defined as the work done per unit charge in moving a charge between two points. Understanding that it's a scalar helps in simplifying calculations in electrical circuits, where direction is not a factor.

The voltage applied across a conductor does not affect its resistance; resistance is determined by the physical properties of the conductor, such as its length, cross-sectional area, and temperature. Understanding these factors helps in selecting materials for electrical applications.

In a series circuit, the resultant resistance is equal to the sum of all individual resistances. This principle is essential for calculating total resistance in series circuits, which affects the current flow throughout the circuit.

Increasing the length of a conductor increases its resistance because the electrons have to travel a longer distance, encountering more collisions along the way. This principle is fundamental in designing electrical circuits and understanding resistance.

Correct Formula: ρ = RA / l

Where:

• ρ = resistivity of the material
• R = resistance of the conductor
• A = cross-sectional area
• l = length of the conductor

Explanation:
Resistivity is a material property that indicates how strongly a material opposes the flow of electric current. Its SI unit is ohm-meter (Ω·m).

Why are other options incorrect:

• a) ρ = l / A → This is incorrect because it ignores resistance and does not correctly define resistivity.

• b) R = ρl / A → This is the formula for resistance, not resistivity; it is derived from the resistivity formula.

• d) R = ρA / l → This is incorrect because in the correct formula for resistance, the length (l) should be in the numerator, not the denominator.

As the temperature of a conductor increases, the resistance typically increases as well due to more frequent collisions between electrons and vibrating ions. This relationship is important for designing circuits that operate under varying thermal conditions.

Conductance is the reciprocal of resistance and represents the ability of a material to conduct electric current. A higher conductance indicates a better conductor, which is important in designing efficient electrical systems.

A non-ohmic resistor does not obey Ohm's Law; its resistance varies with the voltage or current. This behavior is important in applications where variable resistance is needed, such as in thermistors and diodes.

The internal resistance of a cell refers to the resistance that the electrolyte offers to the flow of current. This resistance affects the performance of the cell, particularly during high current draw situations.

A superconductor exhibits zero resistance at very low temperatures, allowing electric current to flow without energy loss. This property can lead to highly efficient power transmission and advanced technologies, potentially revolutionizing many fields.

The SI unit of resistivity is ohm-metre (Ω m). Resistivity is a material property that indicates how much the material resists the flow of electric current, which is pivotal in selecting materials for electrical applications.

The conventional current flow is defined as the flow of positive charge from the positive terminal to the negative terminal. This definition dates back to before the discovery of the electron and remains in use for consistency in circuit analysis.

The potential difference between two points is defined as the work done per unit charge in moving a positive charge from one point to another. This is crucial in understanding how energy is transferred in electrical circuits.