There are three basic circuits
1) Series circuit
2) Parallel circuit
3) Series and  Parallel circuits

Series circuit

Parallel circuit

Series and parallel circuit

Joule’s Law and Power

The heat energy produced by a resistor is

where:

• H is heat energy in joule,
• I is the current in A,
• R is the resistance in ohm, and
• t is time in second.

You can convert joule to calories by multiplying 0.24 on joule.
In a parallel circuit, the least resistance draws the most current and produces the most heat energy because larger current flows through that component.

The rate of using or supplying energy is called power [P]. The power consumption of a resistor is

where:

• [P] is power in watts, [V] is voltage through resistor in volts, [I] is current through resistor in ampere, and
• [R] is resistance in ohms.

Also,
Power [W] = work (energy) / time [t] (unit of work is joule [J] and time[t] is in second).
Therefore,
work or energy [joule] = power [W] * time [t].
The unit for energy is watt-second; watt-minute; and watt-hour.
1 watt-second = 1 joule