Question

An electric blanket uses 21V to heat up when it is switched on. In 5 mins, the blankets circuit transfers 15kJ of energy to the thermal energy store of its surroundings.
Calculate the resistance of the circuit in the electric blanket

Answer 1

we find the current strength from the Joule-Lenz law:

$Q=I\cdot U\cdot t$

$I=\frac{Q}{U\cdot t}= \frac{15000}{21\cdot 300}= 2.38 A$

Then, according to Ohm's law, we find resistance:

$R=\frac{U}{I}=\frac{21}{2.38}=8.82 Ohm$