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Solved problems for the chapter:

Potential Difference and Voltmeters

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Electrical resistance

1. Definitions

2. Ohm's law

3. Kirchhoff's law

3.1. Kirchhoff's first law

3.2. Kirchhoff's second law

4. Total resistance

4.1. Parallel connection of resistors

4.2. Series connection of resistors

5. Resistivity of an electrical conductor

6. Current and voltage measurement

7. Forum

↓ Show theory [1] ↓

Detailed solution steps are available at:

https://en.openprof.com/wb/chapter:potential_difference_and_voltmeters/3634/

Example 1.

Use Ohm's law to calculate the missing quantities and complete the table below.

voltage V	current I	resistance R

Example 2.

Check whether the following statements are correct or not:

Electrical voltage is denoted by the letter V.
The unit of voltage is the Ampere.
Electrical voltage in a circuit is measured using an ammeter.
Driving voltage is the voltage measured against a load in the electrical circuit.

We want to measure the electrical voltage across a lamp. Which voltmeter connection below is correct?

A light bulb and a voltage source are connected to an electrical circuit. The driving voltage in the circuit is 12 V.

What is the voltage across the bulb?
If another identical bulb is connected in series to the circuit, what is the voltage across the first and second bulbs now?

Given two electrical circuits below:

The voltage at the source is 12 V in both circuits. On which lamp do we measure the maximum voltage?

Which of the following statements is/are correct?

Electrical voltage in a circuit is measured using a voltmeter.
The voltage on an electrical element is measured using an ammeter.
We need both an ammeter and a voltmeter to measure the electrical voltage in a circuit.
The electric voltage is denoted by V, and its basic unit is the Ampere.

Which diagram shows the correct connection of the voltmeter when measuring the voltage across a bulb?

In the first and second circuit diagrams, what voltage would the voltmeter read if the driving voltage is 3 V?

How do we know which voltage (DC or AC) is produced by a voltage source?

Indicate which of the following sources produce alternating voltage:

Household socket for electrical appliances.
Battery.
Accumulator.
Potatoes.

10.

Which of the following statements is/are correct?

DC voltage can only be measured with a digital voltmeter.
The voltage value on the digital voltmeter is read directly from the screen.
Digital instruments have a pointer that moves over a measuring scale.
For an accurate reading, we need to look at the analog instrument in line with the pointer on the scale.

11.

Which of the following statements is/are correct?

With an analog voltmeter, it does not matter how we connect the positive and negative terminals across the resistor or voltage source.
An analog voltmeter can damage the pointer due to an incorrectly selected measuring range.
Only DC voltage can be measured with a universal measuring instrument.
The voltage of one section on the voltmeter scale is determined by dividing the total measuring range of the voltmeter by the corresponding number of scale sections.

12.

What is the voltage represented by one small section on the scale of the voltmeter (this is also called the voltmeter constant) in the figure below, if we know that its measuring range cannot be set arbitrarily?

What voltage can be measured with this voltmeter: AC or DC?

13.

Which of the following statements is/are correct?

The voltage of a source is called the driving voltage.
Due to the electric current, a charge flows, and thus an electric voltage is created.
The voltage at a source is equal to 0 V if the electrical circuit is open.
Voltmeter measures the voltage across the load or from the source.

14.

On the scale of a voltmeter, the pointer was initially on the twentieth line. The pointer then moves one section to the right as the voltage increases by 5 V. What voltage does the voltmeter reads?

15.

In the circuits below, a 10 V voltage source is connected in series with a resistor and an open switch. How much voltage would the voltmeter measure in each of the arrangements?

16.

Which quantities is a voltmeter used to measure?

current and e.m.f. only
current and p.d. only
e.m.f. and p.d. only
e.m.f., current and p.d

17.

Which statement about a voltmeter is correct?

It has a scale which is marked in amperes (A).
It must be connected in series in a circuit.
It measures potential difference (p.d.).
It must have three terminals.

18.

Which equation is correct for resistance , potential difference (p.d.) and current ?

19.

Which circuit shows a voltmeter measuring the p.d. across a resistor?

20.

Which unit is equivalent to a volt ()?

21.

Two meters are connected in a circuit to measure the current in a component and the potential difference across the component. Which meters are used and how are they connected to the component?

an ammeter in parallel for current, a voltmeter in series for potential difference
an ammeter in series for current, a voltmeter in parallel for potential difference
a voltmeter in parallel for current, an ammeter in series for potential difference
a voltmeter in series for current, an ammeter in parallel for potential difference

22.

Each diagram shows part of a circuit. The circle represents an instrument used to measure the potential difference (p.d.) across the resistor.

Which row is correct?

	the unit of p.d.	diagram which shows the meter correctly connected
A	amperes	diagram 1
B	amperes	diagram 2
C	volts	diagram 1
D	volts	diagram 2

23.

Which quantity is equivalent to ?

24.

The diagram shows a circuit. The wire between P and Q can be removed and replaced by a circuit component.

Where should a voltmeter be connected to measure the potential difference (p.d.) across the lamp?

between P and Q in place of the wire
in parallel with R and S
in parallel with R and T
in parallel with S and T

25.

Diagram 1 shows a voltmeter that is not connected to anything. It shows a small reading, called a zero error, because it is not correctly adjusted. Diagram 2 shows the same meter used to measure the p.d. across a resistor in a circuit.

What is the p.d. across the resistor?

26.

Three electrical quantities are listed.

potential difference
electromotive force
current

Which quantities are measured in volts?

potential difference only
potential difference and current only
potential difference and electromotive force only
potential difference, electromotive force and current

27.

The resistance of a component in a circuit is found using an ammeter and a voltmeter. How are the ammeter and the voltmeter connected?

the voltmeter and ammeter in parallel with the component
the voltmeter and ammeter in series with the component
the voltmeter in parallel with the component and the ammeter in series with the component
the voltmeter in series with the component and the ammeter in parallel with the component

28.

A teacher asks her class “What quantity can be recorded in volts?”.

Student 1 says “The potential difference across a resistor”.

Student 2 says “The rating of a fuse”.

Student 3 says “The electromotive force of a battery”.

Which students are correct?

1 only
1 and 2
1 and 3
2 and 3

29.

A student investigates the resistance of a lamp. Which row states how the meters must be connected?

	ammeter	voltmeter
A	in parallel with the lamp	in parallel with the lamp
B	in parallel with the lamp	in series with the lamp
C	in series with the lamp	in parallel with the lamp
D	in series with the lamp	in series with the lamp

30.

Which quantity has the same unit as potential difference (p.d.)?

current
electromotive force (e.m.f)
resistance
moment of a force

31.

Which statement about a voltmeter is correct?

A voltmeter measures the current in a component and is connected in series with the component.
A voltmeter measures the current in a component and is connected in parallel with the component.
A voltmeter measures the potential difference (p.d.) across a component and is connected in series with the component.
A voltmeter measures the potential difference (p.d.) across a component and is connected in parallel with the component.

32.

A voltmeter and an ammeter are used to measure the resistance of a resistor. Which diagram shows the voltmeter and the ammeter correctly connected?

33.

The circuit diagram shows a resistor and an resistor connected to a battery.

What is the potential difference (p.d.) across the resistor?

34.

Which row gives the unit for electromotive force (e.m.f.) and the unit for potential difference (p.d.)?

	electromotive force	potential difference
A	newton	joule
B	newton	volt
C	volt	joule
D	volt	volt

35.

When the potential difference (p.d.) across a piece of resistance wire is changed, the current through the wire also changes. The temperature of the wire is kept the same, which graph shows how the p.d. and current are related?