Question

A. In the circuit below, identify how the resistors are connected and then identify the quantity that must always be the same for these resistors.
b. Write two or three sentences to describe what an ammeter measures about a resistor and how it should be connected with the resistor in a circuit.

c. What is the voltage drop across 60.0 Ω resistor that has a 0.300 A current?

d. Draw and label a circuit diagram that has a 24.0 V power supply and two 10.0 Ω resistors connected in a series.

e. What is the equivalent resistance of 3.0 Ω resistor and 2.0 Ω resistor connected in parallel?

f. Describe how a circuit breaker works to protect against household fires.

g. In the circuit below, Identify all resistors that will stop working when the switch is opened. (Second image)

Answer 1

Part a)

When two or more resistors connected across two common terminals then the combination is known as parallel combination

Here in this type of combination potential difference across all resistor will remain same

Part b)

Ammeter is a measuring device which always measure the current in the branch in which it is connected

This is always connected in series along with the branch in which we need to measure the current

Part c)

By ohm's law we know that

$V = iR$

here we know that

i = 0.300 A

R = 60 ohm

$V = (60)(0.300)$

$V = 18 volts$

Part e)

when resistors are in parallel

then we will have

$\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2}$

$\frac{1}{R} = \frac{1}{3} + \frac{1}{2}$

$R = 1.2 ohm$

Part f)

Circuit breaker is a resistance with small melting temperature

When large current flow through the circuit breaker then due to thermal effect it melt down and current stops flowing in the circuit as circuit breaks at that point

So it helps to prevent excess current in the circuit

Part g)

Since switch connected in the branch directly connected to the battery

So here it prevent the current to flow in all three resistors

So all resistors stop to work here

Answer 2

a) The resistors are connected in parallel (they are parallel)

b) The ammeter measures current, so it must be connected in series with the given resistor. Ammeters are very sensitive devices, so you should never connect ammeter across the resistor. It will burn.

c) Ohm's law: V=IR=0.3*60=18 V

d) See the figure

e) $R=\frac{R1\cdot R2}{R1+R2} =1.2$ Ω

f) There is an electromagnet inside with the rotating metal contact that breaks the circuit connected to a spring. With normal working current the magnet cannot attract the contact, when the current is too high, the magnet overcomes spring's tension and breaks the circuit.

g) All three resistors will stop. Imagine that the switch breaks the water. The water will not reach the resistors.