Electric Heating of Mass

When an electric heater heats an object - the electric energy is transformed to heat by increased object temperature. The electric energy used equals the change in thermal energy and can be expressed as:

P t μ = U I t μ

= c m dT                                (1)

electric energy supplied = thermal energy change in object

where

P = power (watts, W)

U = potential difference (volts, V)

I = electrical current (amps, A)

t = time (sec)

μ = heating efficiency

c = specific heat of the heated substance (J/kg^oC)

m = mass of the heated substance (kg)

dT = temperature differance (^oC)

Example - 12 Volt Car Water Heater

The temperature change in a 12 volts and 10 amps Car Water Heater (100% efficient => μ = 1) with 0.4 kg water and 5 minutes heating period can be calculated by modifying (1) to

dT = U I t μ / c m

   = (12 volts) (10 amps) (300 sec) 1 / (4200 J/kg^oC) (0.4 kg)

   = 21.4 ^oC

Note! The mass of the water heater and the heat loss from the heater during heating is neglected in the calculation. In reality the mass of the heater and the heat loss from the heater during the heating process will influence the temperature change.

Electric Heat Calculator

This calculator can be used to calculate temperature rise in an electric heated object or mass. Heat loss during heating is neglected.

P - power (W)

t - time (s) 

  μ - efficiency

c - specific heat (J/kg^oC)

m - mass (kg)

Temperature ^oC
K
^oF

Length m
km
in
ft
yards
miles
naut miles

Area m²
km²
in²
ft²
miles²
acres

Volume m³
liters
in³
ft³
us gal

Weight kg_f
N
lbf

Velocity m/s
km/h
ft/min
ft/s
mph
knots

Pressure Pa
bar
mm H₂O
kg/cm²
psi
inches H₂O

Flow m³/s
m³/h
US gpm
cfm