Heat Transfer in Nature – Formula & Equation Sheet
Essential formulas and equations from Curiosity, tailored for Class 7 in Science.
This one-pager compiles key formulas and equations from the Heat Transfer in Nature chapter of Curiosity. Ideal for exam prep, quick reference, and solving time-bound numerical problems accurately.
Key concepts & formulas
Essential formulas, key terms, and important concepts for quick reference and revision.
Formulas
Q = mcΔT
Q is the heat energy (in joules), m is mass (in kg), c is the specific heat capacity (in J/kg°C), and ΔT is the change in temperature (in °C). This formula calculates the heat absorbed or released by a substance.
E = mc²
E is energy (in joules), m is mass (in kg), and c is the speed of light (≈ 3 × 10⁸ m/s). This formula illustrates the relationship between mass and energy.
V = IR
V is voltage (volts), I is current (amperes), and R is resistance (ohms). This describes Ohm's Law, relating voltage, current, and resistance in a circuit.
h = Q/AΔT
h is the heat transfer coefficient (W/m²K), Q is heat transfer (in watts), A is the area (in m²), and ΔT is the temperature difference (in K). This formula is useful in calculating heat transfer through surfaces.
Q = mL
Q is the heat energy (in joules), m is mass (in kg), and L is the latent heat (in J/kg). This relates to phase changes without a temperature change.
P = A × F
P is pressure (in pascals), A is area (in m²), and F is force (in newtons). This formula helps calculate the pressure exerted on surfaces.
Q = mc(vf - vi)
Q is the heat added, m is mass, vf is final velocity, and vi is initial velocity. Useful when calculating heat resulting from changing states.
R = 1/h
R is thermal resistance (in m²K/W) and h is the heat transfer coefficient. This calculates the resistance to heat transfer through materials.
ΔT = Q/(mc)
ΔT is the change in temperature, Q is heat transfer, m is mass, and c is the specific heat capacity. Useful for understanding temperature change in substances.
h = (k × ΔT × t)/(d)
h is the heat transferred (in joules), k is the thermal conductivity (in W/mK), ΔT is temperature difference, t is time, and d is thickness of the material. This formula relates thermal conductivity to heat transfer.
Equations
Conduction: Q = kAΔT/t
Q is the heat transferred, k is the thermal conductivity, A is the area, ΔT is temperature difference, and t is time. This equation describes heat transfer through conduction.
Convection Equation: Q = mcΔT
Q is the heat transferred, m is mass, c is specific heat, and ΔT is the change in temperature in convection processes.
Stefan-Boltzmann Law: E = σT⁴
E is the energy emitted (W/m²), σ is the Stefan-Boltzmann constant (5.67 x 10⁻⁸ W/m²K⁴), and T is temperature in Kelvin. This equation relates emitted energy to temperature for black bodies.
Ideal Gas Law: PV = nRT
P is pressure (in pascals), V is volume (in m³), n is number of moles, R is the universal gas constant, and T is temperature (in Kelvin). This describes the behavior of ideal gases.
Law of Reflection: θi = θr
θi is the angle of incidence, and θr is the angle of reflection. This principle is essential in understanding how heat radiates.
Frictional Heat: Q = f × d
Q is the heat generated, f is the friction force, and d is the distance. This relates to heat generated through friction.
Time for heat to transfer: t = mL/Q
t is time, m is mass, L is latent heat, and Q is heat transferred. This equation describes how long it takes for a substance to change state.
Latent Heat Transfer Rate: L = Q/m
L is latent heat, Q is heat transferred, and m is mass. This defines the latent heat of a material during phase changes.
Coefficient of Performance: COP = Q_out/W_in
COP is the coefficient of performance, Q_out is the heat extracted from cold reservoir, and W_in is the work input. This is used to assess the efficiency of a heat pump.
Convection Current: V = ΔP/ρg
V is the velocity of convection currents, ΔP is the pressure difference, ρ is the density, and g is the acceleration due to gravity. This describes movement within fluids.
