# Gibilisco:Chapter 1 - Basic Physical Concept

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This is the MCQs for Gibilisco:CHAPTER 1 BASIC PHYSICAL CONCEPT

• 1.

### The atomic number of an element is determined by:

• A.

The number of neutrons.

• B.

The number of protons.

• C.

The number of neutrons plus the number of protons

• D.

The number of electrons.

B. The number of protons.
Explanation
The atomic number of an element is determined by the number of protons in its nucleus. Protons are positively charged particles and each element has a unique number of protons, which is its atomic number. The number of neutrons and electrons can vary in an atom of the same element, but the number of protons remains constant. Therefore, the correct answer is the number of protons.

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• 2.

### The atomic weight of an element is approximately determined by:

• A.

The number of neutrons.

• B.

The number of protons.

• C.

The number of neutrons plus the number of protons.

• D.

The number of electrons.

C. The number of neutrons plus the number of protons.
Explanation
The atomic weight of an element is determined by the sum of the number of neutrons and the number of protons in the nucleus of an atom. The atomic weight is a weighted average of the isotopes of an element, taking into account their abundance. Neutrons and protons have approximately the same mass, so their combined number gives a good estimate of the atomic weight. The number of electrons does not contribute significantly to the atomic weight, as they have much smaller mass compared to neutrons and protons.

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• 3.

### The volt is the standard unit of:

• A.

Current.

• B.

Charge.

• C.

Electromotive force.

• D.

Resistance.

C. Electromotive force.
Explanation
The volt is the standard unit of electromotive force. Electromotive force (EMF) is the measure of the electrical potential difference between two points in a circuit. It represents the force that pushes electric charges through a circuit. The volt is commonly used to measure the voltage or potential difference in electrical systems. It is not the standard unit for current, charge, or resistance.

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• 4.

### A coil has 500 turns and carries 75 mA of current. The magnetomotive force will be:

• A.

37,500 At.

• B.

. 375 At.

• C.

37.5 At.

• D.

3.75 At.

C. 37.5 At.
Explanation
The magnetomotive force is calculated by multiplying the number of turns in the coil by the current flowing through it. In this case, the coil has 500 turns and carries 75 mA of current. Therefore, the magnetomotive force is 500 turns * 75 mA = 37,500 At.

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• 5.

### A ferromagnetic material:

• A.

Concentrates magnetic flux lines within itself.

• B.

Increases the total magnetomotive force around a current-carrying wire.

• C.

Causes an increase in the current in a wire.

• D.

Increases the number of ampere-turns in a wire.

A. Concentrates magnetic flux lines within itself.
Explanation
A ferromagnetic material is able to concentrate magnetic flux lines within itself. This means that when a magnetic field is applied to the material, the magnetic field lines are drawn into the material, making it highly magnetic. This property is what allows ferromagnetic materials to be used in applications such as magnets and transformers.

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• 6.

### Suppose there is an atom of oxygen, containing eight protons and eight neutrons in the nucleus, and two neutrons are added to the nucleus. The resulting atomic weight is about:

• A.

8

• B.

10

• C.

16

• D.

18

D. 18
Explanation
When two neutrons are added to the nucleus of an oxygen atom, the atomic weight increases. Since each neutron has a mass of approximately 1 atomic mass unit (amu), adding two neutrons would increase the atomic weight by 2 amu. Therefore, the resulting atomic weight would be 16 amu (original atomic weight of oxygen) + 2 amu (added neutrons) = 18 amu.

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• 7.

### An isotope:

• A.

Is electrically neutral.

• B.

Has positive electric charge.

• C.

Has negative electric charge.

• D.

Might have either a positive or negative charge.

D. Might have either a positive or negative charge.
Explanation
Isotopes are atoms of the same element that have different numbers of neutrons. Neutrons do not have an electric charge, so adding or removing neutrons does not affect the overall electrical neutrality of the atom. However, isotopes can have different numbers of protons, which determines their electric charge. Therefore, isotopes can have different charges depending on the number of protons they have, and they might have either a positive or negative charge.

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• 8.

### If a material has low resistance:

• A.

It is a good conductor.

• B.

It is a poor conductor.

• C.

The current flows mainly in the form of holes.

• D.

Current can flow only in one direction.

A. It is a good conductor.
Explanation
If a material has low resistance, it means that it allows the flow of electric current easily. This indicates that the material is a good conductor of electricity. Good conductors have a high number of free electrons that are able to move through the material, allowing the current to flow with minimal hindrance.

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• 9.

### In a compound:

• A.

There can be just a single atom of an element.

• B.

There must always be two or more elements.

• C.

The atoms are mixed in with each other but not joined.

• D.

There is always a shortage of electrons.

B. There must always be two or more elements.
Explanation
In a compound, there must always be two or more elements. This is because a compound is formed when two or more different elements chemically combine with each other. The atoms of these elements bond together to form a compound, which has its own unique properties and characteristics. Therefore, a compound cannot consist of just a single element.

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• 10.

### A molecule:

• A.

Might consist of just a single atom of an element.

• B.

Must always contain two or more elements.

• C.

Always has two or more atoms.

• D.

Is always electrically charged.

A. Might consist of just a single atom of an element.
Explanation
A molecule might consist of just a single atom of an element because some elements exist in nature as individual atoms. These atoms can bond with other atoms of the same element to form molecules, but they can also exist independently. Therefore, a molecule does not always have to contain two or more elements or atoms, and it is not always electrically charged.

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• 11.

### An electrical insulator can be made a conductor:

• A.

By heating.

• B.

By cooling.

• C.

By ionizing.

• D.

By oxidizing.

C. By ionizing.
Explanation
An electrical insulator can be made a conductor by ionizing it. Ionization refers to the process of adding or removing electrons from an atom or molecule, resulting in the formation of charged particles called ions. When an insulator is ionized, it gains the ability to conduct electricity because the presence of ions allows the flow of electric charge. This can be achieved by subjecting the insulator to high temperatures, intense radiation, or exposure to certain chemicals that can cause ionization.

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• 12.

### A stroke of lightning:

• A.

Is caused by a movement of holes in an insulator.

• B.

Has a very low current.

• C.

Is a discharge of static electricity.

• D.

Builds up between clouds.

C. Is a discharge of static electricity.
Explanation
A stroke of lightning is a discharge of static electricity. Lightning occurs when there is a buildup of electrical charge in the atmosphere, typically between a cloud and the ground or between two clouds. This buildup of charge is caused by the separation of positive and negative charges within the cloud, creating an imbalance. When the electrical potential difference becomes too great, it causes a rapid discharge of electricity in the form of lightning. This discharge can be extremely powerful and can cause significant damage.

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• 13.

### Of the following substances, the worst conductor is:

• A.

Air.

• B.

Copper.

• C.

Iron.

• D.

Salt water.

A. Air.
Explanation
Air is the worst conductor among the given substances because it is a poor conductor of heat and electricity. Air is a good insulator, meaning it does not allow the easy flow of heat or electricity through it. Copper and iron, on the other hand, are metals that are known for their high conductivity. Salt water, although not as good a conductor as metals, still conducts electricity better than air. Therefore, the correct answer is air.

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• 14.

### A backwards-working electric motor is best described as:

• A.

An inefficient, energy-wasting device.

• B.

A motor with the voltage connected the wrong way.

• C.

An electric generator.

• D.

A magnetic-field generator.

C. An electric generator.
Explanation
A backwards-working electric motor refers to a motor that is functioning in reverse, converting mechanical energy into electrical energy. This is best described as an electric generator, as it is producing electricity rather than consuming it.

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• 15.

### If an EMF of one volt is placed across a resistance of two ohms, then the current is:

• A.

Half an ampere.

• B.

One ampere.

• C.

Two amperes.

• D.

One ohm.

A. Half an ampere.
Explanation
When an EMF of one volt is placed across a resistance of two ohms, according to Ohm's Law (V = IR), the current can be calculated as I = V/R. Substituting the given values, we get I = 1V / 2Î© = 0.5A, which is equal to half an ampere.

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• 16.

### In some batteries, chemical energy can be replenished by:

• A.

Connecting it to a light bulb.

• B.

Charging it.

• C.

Discharging it.

• D.

No means known; when a battery is dead, you have to throw it away.

B. Charging it.
Explanation
Charging a battery replenishes its chemical energy by reversing the chemical reactions that occur during discharging. This process involves applying an external electrical current to the battery, which forces the chemical components inside to return to their original state and store energy for future use.

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• 17.

### An ion:

• A.

Is electrically neutral.

• B.

Has positive electric charge.

• C.

Has negative electric charge.

• D.

Might have either a positive or negative charge.

D. Might have either a positive or negative charge.
Explanation
An ion is an atom or molecule that has gained or lost electrons, resulting in a positive or negative charge. This means that ions can have either a positive or negative electric charge, depending on whether they have gained or lost electrons. Therefore, the correct answer is that an ion might have either a positive or negative charge.

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• 18.

### Movement of holes in a semiconductor:

• A.

Is like a flow of electrons in the same direction.

• B.

Is possible only if the current is high enough.

• C.

Results in a certain amount of electric current.

• D.

Causes the material to stop conducting.

C. Results in a certain amount of electric current.
Explanation
The movement of holes in a semiconductor results in a certain amount of electric current. In a semiconductor, when an electron moves from one atom to another, it leaves behind a hole in the original atom. These holes can move through the crystal lattice, creating a flow of positive charge. This movement of holes contributes to the overall electric current in the semiconductor material.

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• 19.

### Of the following substances, the best conductor is:

• A.

Air.

• B.

Copper.

• C.

Iron.

• D.

Salt water.

B. Copper.
Explanation
Copper is the best conductor among the given substances because it has a high electrical conductivity. Copper is widely used in electrical wiring and other electrical components due to its ability to efficiently conduct electricity. Air, iron, and salt water have lower conductivity compared to copper, making copper the best choice in terms of conducting electricity.

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• 20.

### A coulomb:

• A.

Represents a current of one ampere.

• B.

Flows through a 100-watt light bulb.

• C.

Is one ampere per second.

• D.

Is an extremely large number of charge carriers.

D. Is an extremely large number of charge carriers.
Explanation
The answer "Is an extremely large number of charge carriers" is correct because a coulomb is a unit of electric charge, and it represents a large amount of charge. One coulomb is equal to the charge of approximately 6.24 x 10^18 electrons or other elementary charged particles. Therefore, it is an extremely large number of charge carriers. The other options are incorrect as they do not accurately describe the definition or measurement of a coulomb.

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• Mar 22, 2023
Quiz Edited by
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• Oct 20, 2013
Quiz Created by
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