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RRB ALP Heat & Temperature

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This page covers RRB ALP Heat & Temperature with complete concept notes, 12 graded practice MCQs, key points and exam-specific tips. Free to study.

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Concept Notes

Heat & Temperature— Rules & Concept

Core ConceptRead this first — the foundation of the topic

HEAT & TEMPERATURE — CORE CONCEPT Heat and Temperature are two different things. Students often confuse them. Let us understand both clearly.

Heat is a form of energy. It flows from a hotter object to a cooler object. Heat is measured in Joules (J) or Calories (cal). 1 calorie = 4.2 Joules. Temperature is the measure of how hot or cold an object is. It tells us the degree of hotness. Temperature is measured in Celsius (°C), Fahrenheit (°F), or Kelvin (K).

Key RulesCore rules you must know cold
Example

A large bucket of water at 30°C has more heat energy than a small cup of water at 80°C. 4. Specific Heat Capacity (s) — This is the amount of heat needed to raise the temperature of 1 kg of a substance by 1°C. Water has the highest specific heat = 4200 J/kg°C. This is why water is used as a coolant. 5

Heat always flows by three methods

Conduction (solids), Convection (liquids and gases), Radiation (no medium needed — like sunlight).

Formula BlockMemorise — at least one formula appears in every paper
Heat Formula: Q = m × s × ΔT

Where:

Q = Heat energy (in Joules)
m = Mass of substance (in kg)
s = Specific heat capacity (in J/kg°C)
ΔT = Change in temperature (Final Temp − Initial Temp)

Temperature Conversion Formulas:

°C to °F → F = (9/5 × C) + 32
°F to °C → C = 5/9 × (F − 32)
°C to K → K = C + 273
K to °C → C = K − 273
Note: 0°C = 273 K = 32°F. Absolute Zero = 0 K = −273°C.
Exam PatternsWhat examiners ask — read before attempting PYQs

RRB Group D commonly asks: - Direct conversion between Celsius, Fahrenheit, and Kelvin -

When to UseQuickly decide which method to apply in the exam

of heat transfer applies to a situation (sun heating earth = Radiation) - Specific heat of water based problems - Finding Q using the formula Q = msΔT - Comparing heat content vs temperature SHORTCUT / TRICK Trick 1 — Temperature Conversion

Memory HookRemember this — never confuse the two again

To convert Celsius to Fahrenheit, remember: Double it, subtract 10%, add 32. Example: 100°C → Double = 200, subtract 10% = 180, add 32 = 212°F. ✓ Fast and accurate! Trick 2 — Kelvin is always POSITIVE. If any option shows a negative Kelvin value, reject it immediately. Minimum Kelvin = 0 K (Absolute Zero).

Worked ExampleSolve this step-by-step before moving on
1
Step 1

Write the formula → Q = m × s × ΔT

2
Step 2

Find ΔT = 70 − 20 = 50°C

3
Step 3

Put values → Q = 2 × 4200 × 50

4
Step 4

Calculate → Q = 420,000 J = 4.2 × 10⁵ J Answer: 4,20,000 Joules or 420 kJ

Exam TrapsCommon mistakes students make — avoid these

Students mix up Heat and Temperature. Remember: A large cold object can have MORE heat energy than a small hot object. Heat depends on mass AND specific heat AND temperature.

Temperature alone does not decide heat content. Also, never forget to add 273 when converting °C to Kelvin — losing that step costs marks.

Key Points to Remember

  • Heat is energy measured in Joules; Temperature is degree of hotness measured in °C, °F, or Kelvin.
  • Heat always flows from higher temperature to lower temperature — never the other way.
  • Formula: Q = m × s × ΔT, where Q = heat, m = mass, s = specific heat, ΔT = temperature change.
  • Specific heat of water = 4200 J/kg°C — highest among common substances, making it ideal as a coolant.
  • Temperature conversion: °C to K = add 273; °C to °F = multiply by 9/5 then add 32.
  • Absolute Zero = 0 Kelvin = −273°C — the lowest possible temperature; no negative Kelvin exists.
  • Three modes of heat transfer: Conduction (solids), Convection (liquids/gases), Radiation (no medium needed).
  • Thermal Equilibrium occurs when two bodies reach the same temperature and heat exchange stops.

Exam-Specific Tips

  • Specific heat capacity of water = 4200 J/kg°C (or 1 cal/g°C) — highest among common substances.
  • 1 Calorie = 4.2 Joules (this conversion is directly asked in MCQs).
  • Absolute Zero = 0 Kelvin = −273°C — below this temperature, nothing can exist.
  • 0°C = 273 K = 32°F — this three-way equivalence is a favourite exam fact.
  • 100°C = 373 K = 212°F — the boiling point of water in all three scales.
  • Radiation is the only mode of heat transfer that does not need any medium — this is how the Sun heats the Earth.
  • Normal human body temperature = 37°C = 98.6°F = 310 K.
  • Mercury thermometers measure temperature because mercury expands uniformly with heat and has a wide liquid range (−39°C to 357°C).
Practice MCQs

Heat & Temperature — Practice Questions

12graded MCQs · easy to hard · full solution & trap analysis

All MCQs →
Practice 1easy

What is the specific heat capacity?

Practice 2easy

A metal rod is heated from 25°C to 75°C. What is the change in temperature in Kelvin?

Practice 3easy

Which of the following is the correct relationship between heat and temperature?

Practice 4easy

At what temperature are the Celsius and Fahrenheit scales equal?

Practice 5medium

An object absorbs 5000 J of heat and its temperature rises from 20°C to 40°C. If the mass of the object is 2 kg, its specific heat capacity is:

Practice 6medium

The temperature at which the density of water is maximum is:

Practice 7medium

If the temperature of a gas is increased from 27°C to 127°C at constant volume, the pressure will increase by a factor of:

Practice 8medium

A steel rod of length 1 m is heated from 0°C to 50°C. If the coefficient of linear expansion is 12 × 10⁻⁶ per °C, the increase in length will be approximately:

Practice 9medium

The specific heat capacity of a substance is defined as the amount of heat required to:

Practice 10hard

The specific heat capacity of water is 4200 J/kg·K. If 2 kg of water is heated from 25°C to 75°C, how much heat energy is required?

Practice 11hard

Two objects A and B are in thermal contact. Object A is at 50°C and object B is at 30°C. Heat flows from A to B until thermal equilibrium is reached. Which statement is correct?

Practice 12hard

A metal rod is heated from 20°C to 80°C. If the coefficient of linear expansion of the metal is 1.2 × 10⁻⁵ K⁻¹ and the original length is 2 m, what is the increase in length of the rod?

60-Second Revision — Heat & Temperature

  • Formula: Q = m × s × ΔT — memorise the order: mass × specific heat × temperature change.
  • Remember: °C to K → add 273; K to °C → subtract 273. Never skip this step.
  • Trick: To convert °C to °F quickly → double the °C, subtract 10%, then add 32.
  • Trap: High temperature does NOT mean more heat — heat also depends on mass and specific heat capacity.
  • Remember: Water has specific heat 4200 J/kg°C — highest of common substances, used as coolant in engines.
  • Three heat transfer modes — Conduction (solid), Convection (liquid/gas), Radiation (no medium) — Sun uses Radiation.
  • Absolute Zero = 0 K = −273°C. Any MCQ option showing negative Kelvin is always WRONG — eliminate immediately.
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