General Q&A for Class 12 · Page 161
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is the simple form of Ohm's Law?
The simplest form of Ohm's Law is V = IR (voltage equals current times resistance). This concise equation captures the fundamental relationship between the three basic electrical properties in any circuit.
- GeneralClass 12All
Which resistance is higher?
Higher resistance means greater opposition to current flow. Insulators like rubber, glass, and plastic have very high resistance (megohms to gigohms). Conductors like copper and aluminum have very low resistance. In circuit design, "higher resistance" is relative a 1000-ohm resistor is higher than a 100-ohm resistor.
- GeneralClass 12All
How do you test a circuit?
To test a circuit: First, disconnect power for safety. Use a multimeter to check resistance (ohms) to verify connections and component values. Then apply power and measure voltage across components and current through the circuit. Compare readings to expected values using Ohm's Law. Look for opens (infinite resistance), shorts (zero resistance where there shouldn't be), or incorrect values.
- GeneralClass 12All
How many ohms is good?
The "good" resistance value depends entirely on the application. For wires and connections, near 0 ohms is ideal. For resistors, the correct value matches the circuit design (could be anywhere from a fraction of an ohm to millions of ohms). For insulation, you want very high resistance (megohms). Context determines what's appropriate.
- GeneralClass 12All
What is the full name of Ohm's Law?
Ohm's Law doesn't have a longer "full name" it's simply called "Ohm's Law" after its discoverer. Sometimes it's formally stated as "Ohm's Law of Electrical Resistance" to distinguish it from other scientific laws, but "Ohm's Law" is the standard terminology.
- GeneralClass 12All
How do you calculate volts to ohms?
You cannot directly convert volts to ohms because they measure different properties. However, if you know the current, you can find resistance: R = V ÷ I. For example, with 12 volts and 3 amperes, the resistance is 12V ÷ 3A = 4 ohms.
- GeneralClass 12All
What are the 3 formulas of electricity?
The three fundamental electrical formulas are: Ohm's Law: V = I × R (relating voltage, current, and resistance) Power formula: P = V × I (relating power, voltage, and current) Joule's Law: P = I² × R (relating power dissipation to current and resistance) These formulas can be combined and rearranged to solve virtually any basic electrical circuit problem.
- GeneralClass 12All
Why test for ohms?
Testing for ohms (resistance) helps diagnose electrical problems. It identifies broken wires (infinite resistance), short circuits (near-zero resistance), faulty components, and degraded connections. Resistance testing ensures circuits are safe before applying power and helps verify that components meet specifications.
- GeneralClass 12All
How many ohms is a bad wire?
A good wire typically has very low resistance (near 0 ohms, usually under 1 ohm for short runs). A bad or broken wire shows infinite resistance (often displayed as "OL" for overload on a multimeter). If a wire shows several ohms or more where it should be near zero, it indicates damage, corrosion, or poor connections
- GeneralClass 12All
Who uses Ohm's Law?
Electricians, electrical engineers, electronics technicians, circuit designers, automotive technicians, HVAC technicians, and anyone working with electrical systems use Ohm's Law daily. It's essential for students learning electronics, hobbyists building projects, and professionals maintaining electrical equipment.
- GeneralClass 12All
Is mass a formula unit?
No, mass is not a formula unit. A formula unit is the smallest whole-number ratio of ions in an ionic compound (like NaCl). Formula mass is the sum of atomic masses in one formula unit. Mass itself is a physical property measured in grams or kilograms.
- GeneralClass 12All
Are formula units mass?
Formula units are not mass, but they have formula mass. A formula unit represents the simplest ratio of elements in an ionic compound. The formula mass is calculated by adding the atomic masses of all atoms in that formula unit and is expressed in atomic mass units (amu) or grams per mole.
- GeneralClass 12All
Why is formula mass?
Formula mass exists to quantify the mass of one formula unit of an ionic compound. It's calculated by summing the atomic masses of all atoms in the chemical formula. For example, NaCl has a formula mass of about 58.5 amu (Na = 23 + Cl = 35.5). This helps chemists perform stoichiometric calculations and understand compound composition.
- GeneralClass 12All
How to calculate mass and weight?
To calculate mass: From density: Mass = Density × Volume From weight: Mass = Weight ÷ 9.8 (on Earth) Direct measurement: Use a balance or scale To calculate weight: Weight = Mass × Gravitational acceleration On Earth: Weight (N) = Mass (kg) × 9.8 m/s² Remember that mass is measured in kg, while weight is measured in Newtons.
- GeneralClass 12All
What is 1 SI unit?
"1 SI unit" refers to one unit from the International System of Units (SI), the modern metric system. For mass, 1 SI unit = 1 kilogram (kg). The SI includes seven base units: meter (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), and candela (light intensity).
- GeneralClass 12All
What is 1 unit equal to?
The value of "1 unit" depends on context: Electrical energy: 1 unit = 1 kilowatt-hour (kWh) Mass: 1 unit typically means 1 kilogram General: Defined by the specific measurement system being used Always check the context to understand what "unit" refers to in any given situation.
- GeneralClass 12All
How much is 1 unit mass?
1 unit mass typically refers to 1 kilogram in the metric system, or 1 gram in chemistry. In atomic physics, 1 atomic mass unit (amu) equals approximately 1.66 × 10⁻²⁷ kg. The specific value depends on the measurement system being referenced.
- GeneralClass 12All
How to calculate unit mass?
Unit mass typically means mass per single unit or item: Unit mass = Total mass ÷ Number of units For example, if 10 apples have a total mass of 2 kg, the unit mass per apple is 2 kg ÷ 10 = 0.2 kg (200g). This concept helps in pricing, packaging, and manufacturing.
- GeneralClass 12All
What is an example of Ohm's Law?
A practical example: Your smartphone charger outputs 5 volts, and your phone's charging circuit has 2.5 ohms of resistance. Using I = V ÷ R, the charging current is 5V ÷ 2.5Ω = 2 amperes. This explains why your phone charges at a specific rate based on the charger's voltage and the device's internal resistance.
- GeneralClass 12All
What is resistance in Ohm's Law?
Resistance is the opposition to current flow in a circuit, measured in ohms (Ω). In Ohm's Law, resistance is calculated as R = V ÷ I. Different materials have different resistance levels—copper has low resistance (good conductor), while rubber has high resistance (good insulator). Resistance converts electrical energy into heat.