# Current Electricity - Basic Electrical Engineering MCQs Part-1

1. If the three color bands of resister are red, orange and yellow. then the value of resistance is
A. 240 mega Ohm
B. 230 mega ohm
C. 22 mega ohm
D. 21 mega ohm

Explanation:
Here color bands for resister are Red, orange and yellow
first we know about the color code of resister

Color code for resister value
• Black -- 0
• Brown -- 1
• Red -- 2
• Orange --3
• Yellow --4
• Green --5
• Blue --6
• Violet --7
• Grey --8
• White --9

Color code for tolerance
• Gold-- 5%
• Silver -- 10 %
• No Color -- 20 %

Take Digit for first and second color and take number of zero for third digit

Here given color are red --2 orange --3 & yellow --4 nos of zero

Value of resistance is 230000 Ohm called it 230 mega ohm.

2. Which have negative temperature of coefficient resistance ?
A. Copper
B. Aluminum
C. Brass
D. Insulators

Explanation:
Insulator have negative temperature of coefficient resistance.

3. Electrical Heater is rated as 3000W ,230V then the value of heater coil is
A. 17.7 ohm.
B. 17.6 ohm
C. 17.2 Ohm
D. 17.3 ohm

Explanation :
Here here wattage of heater are given that 3000W and voltage is Given that 230V

formula Power P = v2/ R

Here P = 3000 W

V = 230 V

R = ?

so Formula become

R = v2 / P
R = 230 * 230 / 3000
R = 52900 / 3000
R = 17.6 ohm

4. The S.L. unit of power is
A. henry
B. coulomb
C. watt
D. watt-hour

Explanation:
• The SI unit of electric power is the watt (W).
• The rate at which electric energy is dissipated or consumed in an electric circuit is termed as electric power.
• The power P is given by, P = VI.
• The SI unit of electric power is the watt (W). It is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.
• Columb-The SI unit of electric charge.
• Ampere-The electric current is expressed by a unit called ampere.
• Joule-The SI unit of energy is the joule.

5. Electric pressure is also called
A. resistance
B. power
C. voltage
D. energy

Explanation:
Electric pressure is also called as voltage or electrical potential. One volt is the amount of pressure required to cause one ampere of current to flow against one ohm of resistance.

Electrical pressure:
• The difference in electric potential between the two points is called electrical pressure is also known as voltage.
• The unit of electrical pressure is Volt(V) .
•  1 volt is the amount of pressure required to flow one ampere of electricity through one ohm of resistance.

Voltage:
The difference in the electric potential between the two points is known as voltage. It is the effort expended in transporting a charge from one pole to another via a wire.

Mathematically, it is represented as:
V = IR

Here,
V is the voltage measured in Volts .
I is the current measured in Amperes .
R is the resistance measured in ohms.

6. The substances which have a large number of free electrons and offer a low resistance are called
A. insulators
B. inductors
C. semi-conductors
D. conductors

Explanation:
• The substances which have many free electrons and offer very low resistance are called conductors.
• The substances which cannot pass a current under normal conditions are known as insulators. The resistance of an insulator is usually high. Insulators have no free electrons.

Insulators:
• These are the substances that do not conduct electricity.
• The energy gap between the conduction band and the valence band is so vast that they do not conduct flow of charges easily.

Inductor:
• It is basically a coil, when connected to an emf generates back emf by electromagnetic induction.
• It allows the flow of current through it only in a steady state of current.

Semiconductors:
• These are substances that conduct electricity at suitable temperatures .
• This is because the electrons gain sufficient thermal energy to overcome the gap between the conduction and valence band.
• Normally there are no electrons in the conduction band of semiconductors.

Conductors:
• These substances conduct electricity at any given temperatures.
• Normally there are sufficient electrons in the conduction band as their conduction and the valence band overlap with each other i.e. metals.
• It is to be noted that the conduction of the semiconductors increases with increase in temperature.
• Whereas for metals the conduction increases with the decrease in temperature.
• At a particular lower temperature the metals can offer zero resistance, such substances are called superconductors.

7. Out of the following which is not a poor conductor ?
A. Cast iron
B. Copper
C.  Carbon
D. Tungsten

Explanation:
• Metals are good conductors of heat and electricity.
• Copper is a 3d block transition metal and it is a good conductor of heat and electricity.
• Again cast iron, and tungsten is poor conductors of heat and electricity.
• Carbon is a non-metal and poor conductor of heat and electricity.

8. Out of the following which is an insulating material ?
A. Copper
B. Gold
C. Silver
D. Paper

Explanation:
Some of the commonly used insulation materials in homes include the following: rock wool, slag wool cellulose, glass wool, paper, polystyrene, urethane foam, vermiculite, perlite, wood fiber, and plant fiber.

9. Which of the following materials is an electric insulator?
A Aluminum
B Gold
C Rubber
D all of these

Explanation:
• An electric insulator is a material which exhibits high resistivity to the flow of current through it.
• They have strongly bound electrons in their atoms, which do not tend to move freely to facilitate the flow of electricity.
• The most common examples of insulators are non-metals.
• Electric insulators are materials with strongly bound electrons in their atoms.
• Due to this, charges present in the atoms of these materials are not free to move randomly and thus, they do not tend to conduct electricity easily.
• Clearly, insulators are said to have high resistivity to the flow of electric current.
• The most common examples of insulators are non-metals. Some other good insulators are paper, Teflon and glass.
• Non-metals are the materials which have entirely different properties than those of metals.
• For example, most of the non-metals have low melting-point, boiling point, density and poor thermal conductivity. As already mentioned, they also have poor electrical conductivity.
• Some of the examples of non-metals are oxygen(gas), bromine(liquid), carbon(solid) and germanium(metalloid).

10. The property of a conductor due to which it passes current is called
A. resistance
B. reluctance
C. conductance
D. inductance