Recent questions and answers in Physics

State Newton's First Law of Motion, also known as the law of inertia.

Given n resistors each of resistance R, how will you combine them to get the (i) maximum (ii) minimum effective resistance? What is the ratio of the maximum to minimum resistance?
Answer : The two fundamental ways to combine resistors are in **series** and in **parallel**. These two configurations yield the maximum and minimum possible resistances, respectively. --- ### (i) Maximum Effective Resistance To obtain the * ... {min} = R/n$ | | **Ratio** | $R_{max} / R_{min}$ | $n^2$ |...

A high tension (HT) supply of, say, 6 kV must have a very large internal resistance. Why?
Answer : The primary reason is **safety and current limiting**. Let's use Ohm's Law ($V = IR$) to understand this. A power supply can be modeled as an ideal voltage source ($V_s$) in series ... HT supply for **power transmission** has a very low internal resistance for **efficiency and power delivery**....

A low voltage supply from which one needs high currents must have very low internal resistance. Why?
Answer : ### The Simple Analogy: A Water Pipe Imagine your power supply is a large water tank (representing the voltage) and you need to get a high flow of water (high current) out of a pipe at ... extremely small, this will generate a massive amount of heat, which can damage or destroy the power supply....

Is ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law.
Answer : The answer is no, **Ohm's law is not universally applicable for all conducting elements.** Ohm's law is an empirical rule, not a fundamental law of nature. It accurately describes the ... under stable conditions, but it is far from a universal law for all materials that conduct electricity....

A steady current flow in a metallic conductor of non-uniform crosssection. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?
Answer : Here is a detailed explanation for each quantity: ### 1. Current (I) * **Why it's constant:** The term "steady current" implies that the rate of flow of charge ($I = dQ/dt$) is constant. Due to the ... ($v_d$)** | Not Constant | $v_d = I/(nAe)$. Since A is not constant, $v_d$ is not constant. |...

Six lead-acid type of secondary cells each of emf 2.0 V and internal resistance 0.015 Ohm are joined in series to provide a supply to a resistance of 8.5 Ohm . What is the current drawn from the supply and its terminal voltage?
Answer : ### Given Data: * Number of cells, **n = 6** * EMF of each cell, **E_cell = 2.0 V** * Internal resistance of each cell, **r_cell = 0.015 Ω** * External resistance (load), **R = 8.5 Ω ... The current drawn from the supply is **1.40 A**. * The terminal voltage of the supply is **11.9 V**....

A storage battery of emf 8.0 V and internal resistance 0.5 Ohm is being charged by a 120 V DC supply using a series resistor of 15.5 Ohm . What is the terminal voltage of the battery during charging? What is the purpose of having a series resistor in the charging circuit?
Answer : ### Given Data: * Electromotive force (emf) of the battery, $E = 8.0 \text{ V}$ * Internal resistance of the battery, $r = 0.5 \text{ } \Omega$ * DC supply voltage, $V_{supply} = ... to a much safer and more manageable **7.0 A**, protecting both the battery and the power supply from damage....

A silver wire has a resistance of 2.1 Ohm at 27.5 degree C , and a resistance of 2.7 Ohm at 100 degree C . Determine the temperature coefficient of resistivity of silver.
Answer : ### 1. Understand the Principle The relationship between resistance and temperature for most metals (like silver) over a moderate temperature range is approximately linear and can be described by the formula: $R_2 = ... 00394 °C⁻¹** Alternatively, in scientific notation: **α = 3.94 x 10⁻³ °C⁻¹**...

Three resistors 1 Ohm , 2 Ohm and 3 Ohm are combined in series. What is the total resistance of the combination?
Answer : When resistors are combined in series, the total resistance is the sum of the individual resistances. The formula is: R_total = R1 + R2 + R3 Given the values: * R1 = 1 Ω * R2 = 2 Ω * R3 = 3 Ω ... = 1 Ω + 2 Ω + 3 Ω = 6 Ω So, the total resistance of the combination is **6 Ohms**....