Question

(a)The following resistors are in parallel: 1000, 800, 500, 200, and 100 (. What is the total resistance?

(b) What resistance value in parallel with 100 ( produces a total resistance of 40 (?

(a) A 10 ( resistor, a 11 ( resistor and a 39 ( resistor are connected in series across a potential difference of 120 V. Calculate the voltage drop across the 10 ( resistor.

(b) Three resistors, whose values are 35 (, 45 (, and 85 (, are connected in parallel across a 35 V battery. What is the current through the 35 ( resistor

Answer 1

• Calculations3

1.a)

$\qquad\qquad \begin{aligned} \small \frac{1}{R_e}&=\small \frac{1}{1000}+\frac{1}{800}+\frac{1}{500}+\frac{1}{200}+\frac{1}{100}\\ \small R_e&=\small 51.9\,\Omega \end{aligned}$

b)

$\qquad\qquad \begin{aligned} \small \frac{1}{40}&=\small \frac{1}{R}+\frac{1}{51.9}\\ \small R&=\small 174.5\,\Omega \end{aligned}$

1.a)

$\qquad\qquad \begin{aligned} \small i&=\small \frac{V}{R_{total}}=\frac{120V}{(10+11+39)\Omega}\\ &=\small 2\,A\\ \\ \small V_{10}&=\small2A\times10\Omega\\ &=\small 20\,V \end{aligned}$

b)

• The 35V potential is common to each resistor. Therefore, v = iR can be applied individually.

$\qquad\qquad \begin{aligned} \small i_{35}&=\small \frac{35V}{35\Omega}\\ &=\small 1\,A \end{aligned}$