Question

If three resistor are connected in series, what is the voltage drop in R1 if the value of R1= 12 ohm R2 = 20 ohm R3 = 5 ohm and the voltage source is Et = 24 volts

Answer 1

The total resistance is the sum of the individual resistances

$$R=R_1+R_2+R_3$$

$$I=\dfrac{E_t}{R_1+R_2+R_3}$$

The voltage drop in $R_1$ is

$$U_1=IR_1=\dfrac{R_1}{R_1+R_2+R_3}E_t$$

$$U_1=\dfrac{12\ Ohm}{12\ Ohm+20\ Ohm+5\ Ohm}\cdot24 \ V$$

$$=\dfrac{288}{37}\ V\approx7.784\ V$$