The question asks to identify the type of substances that maintain a constant resistance across a wide range of applied voltages. This directly relates to Ohm's Law and the classification of materials based on their electrical behavior.
Correct Option: A) Ohmic substances are those that obey Ohm's Law, meaning their resistance remains constant over a wide range of applied voltages and resulting currents. Examples include most metals at constant temperature.
A resistor having resistance 6.2Ω is connected across a battery of 5 V. The current passing through the resistor is
This problem can be solved using Ohm's Law, which relates voltage (V), current (I), and resistance (R) in an electrical circuit. Ohm's Law is given by the formula \(V = I \times R\).
Correct Option: B) 0.8 A
The question asks about the relationship between the length of a wire and its resistance. To answer this, we need to recall the formula for electrical resistance, which relates resistance to the material's resistivity, length, and cross-sectional area.
Correct Option: D) More resistance — As derived from the formula \(R = \rho \frac{L}{A}\), resistance is directly proportional to the length of the wire. Therefore, longer wires have more resistance than shorter wires, assuming they are made of the same material and have the same cross-sectional area.
The question asks for a device that automatically disconnects the electrical supply when the current exceeds a safe or normal value. This is a fundamental safety function in electrical systems to prevent damage to equipment and reduce fire hazards. We need to evaluate each option based on its primary function.
B) Circuit breaker — A circuit breaker is specifically designed to automatically interrupt an electrical circuit when an overcurrent or short circuit condition is detected. It is a resettable device, making it an ideal choice for automatic disconnection and protection.
This question tests the fundamental understanding of Ohm's Law, which describes the relationship between voltage (potential difference), current, and resistance in an electrical circuit. We need to recall the standard mathematical formulation of Ohm's Law.
Correct Option: C) I (current) × R (resistance)
The question asks about the relationship between the resistance of a conductor and various physical properties. We need to recall the formula for the resistance of a conductor and analyze how it depends on each given option.
The resistance \(R\) of a conductor is given by the formula:
\[ R = \rho \frac{L}{A} \]Where:
From this formula, we can observe the relationship between resistance and each variable:
The question asks which factor the resistance varies inversely as. Based on our analysis, resistance varies inversely as the area of cross-section.
B) Area of cross-section — As derived from the formula \(R = \rho \frac{L}{A}\), the resistance \(R\) is inversely proportional to the area of cross-section \(A\). This means if the area of cross-section increases, the resistance decreases, and vice versa.