The formula to calculate the total resistance of a parallel circuit is:
Where are the individual resistances
Let's now apply the formula to each circuit:
A.
A parallel circuit with a 20-ohm resistor and a 10-ohm resistor.
The equivalent resistance is:
B.
A parallel circuit with two 20-ohm resistors and a 10-ohm resistor
The equivalent resistance is:
C.
A parallel circuit with a 15-ohm light bulb and a 20-ohm resistor.
The equivalent resistance is:
D.
A parallel circuit with two 100-ohm resistors and a 20-ohm resistor.
The equivalent resistance is:
E.
A parallel circuit with a 10-ohm, 20-ohm, 100-ohm and 200-ohm resistor.
The equivalent resistance is: