Electricity - Practice Test, Class 10 Science - Class 10 MCQ

• SI unit of electric charge: The SI unit of electric charge is the coulomb (C). It is named after the French physicist Charles-Augustin de Coulomb.


• Definition of Coulomb: One coulomb is defined as the amount of electric charge that flows past a point in one second when there is a current of one ampere.


• Relationship with other units: The coulomb is related to the ampere (A) through the equation Q = I * t, where Q is the charge in coulombs, I is the current in amperes, and t is the time in seconds.


• Importance: The coulomb is a fundamental unit in electromagnetism and is used to quantify the amount of electric charge in various systems.

• Step 1: Choose the appropriate measuring instrument


• Step 2: Connect the voltmeter to the two terminals


• Step 3: Read the measurement displayed on the voltmeter

• Ammeter: Measures current flowing through a circuit, not potential difference


• Voltmeter: Specifically designed to measure potential difference in volts


• Ohm-meter: Measures resistance in a circuit, not potential difference


• Rheostat: Used to vary the current in a circuit, not measure potential difference

Therefore, the correct instrument to measure potential difference between two terminals is a voltmeter. It is specifically designed for this purpose and provides accurate readings of the voltage difference.

• Detect direction of current: A galvanometer is primarily used to detect the direction of current flowing through a circuit. It does this by measuring the flow of electric current in a particular direction.

• When current flows through a galvanometer, it causes a deflection of the needle in a specific direction, indicating the direction of the current.


• Galvanometers are sensitive instruments that can detect even small currents, making them useful for various applications in electrical circuits.


• While galvanometers can be used to measure potential difference and the amount of current flowing, their primary function is to detect the direction of current.


• Galvanometers are commonly used in ammeters and voltmeters to indicate the presence and direction of electric current.

• Definition: The rate of flow of an electric charge is known as electric current.


• Symbol: It is represented by the symbol 'I' in equations.


• Unit: The SI unit of electric current is ampere (A).


• Formula: Electric current (I) = Charge (Q) / Time (t)


• Direction: Electric current flows from positive to negative in a circuit.


• Conductance: Electric conductance (not to be confused with current) is the ability of a material to conduct electric current.

• Functionality: Electric current is essential for the operation of electrical devices and circuits.


• Applications: It is used in various applications such as lighting, heating, and powering electronic devices.


• Measurement: Current is measured using an ammeter, which is connected in series in a circuit.


• Control: Controlling the flow of current is crucial for safety and efficient operation of electrical systems.

• Scientist involved: Ohm


• Explanation: The relation between potential difference (V) and current (I) was discovered by the German physicist Georg Simon Ohm. Ohm's law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points.


• Ohm's law formula: Mathematically, Ohm's law is represented as V = IR, where V is the potential difference, I is the current, and R is the resistance of the conductor.


• Experimental verification: Ohm formulated this law based on his experiments with electrical circuits and conductors. He found that the current flowing through a conductor is directly proportional to the potential difference applied across it, provided the temperature and other physical conditions remain constant.


• Significance: Ohm's law is a fundamental principle in electrical engineering and is used to analyze and design electrical circuits. It allows engineers to predict the behavior of circuits and determine the relationship between voltage, current, and resistance.

• Definition: Resistance is the measure of opposition to the flow of electric current in a circuit.


• Ohm's Law: Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.


• Mathematical Representation: Resistance (R) is calculated by dividing the voltage (V) by the current (I), R = V/I.


• SI Unit: The SI unit of resistance is Ohm, represented by the symbol Ω.


• Named After: The unit Ohm is named after the German physicist Georg Simon Ohm.

Therefore, the correct answer to the question is B: Ohm.

• Current (I) = 2A


• Potential difference (V) = 4V

• Ohm's Law: V = IR

• Using Ohm's Law, we can calculate the resistance (R) of the conductor.


• Substitute the given values into the formula: 4V = 2A * R


• Solve for R: R = 4V / 2A = 2 Ω

• The resistance of the conductor is 2 Ω.

• Voltmeter: This apparatus is used to measure the voltage across the circuit components.


• Ammeter: This device is used to measure the current flowing through the circuit.


• Galvanometer: This apparatus is not typically used during the verification of Ohm's law as it is more commonly used for detecting small currents rather than measuring and verifying Ohm's law.


• Rheostat: This device is used to vary the resistance in the circuit, allowing for different resistance values to be tested in accordance with Ohm's law.

Therefore, the correct answer is C: Galvanometer, as it is not a commonly used apparatus for verifying Ohm's law.

• Direct Relationship: There is a direct relationship between temperature and resistance of a conductor.


• Increase in Temperature: As the temperature of a conductor increases, its resistance also increases.


• Explanation: When the temperature of a conductor rises, the atoms in the conductor vibrate more vigorously, causing more collisions with the free electrons. This increased collision results in greater opposition to the flow of current, leading to an increase in resistance.


• Ohm's Law: According to Ohm's Law, resistance (R) is directly proportional to temperature (T) for most conductors.


• Exceptions: There are some materials like semiconductors that exhibit a decrease in resistance with an increase in temperature, known as negative temperature coefficient materials.


• Conclusion: In general, the resistance of a conductor increases with an increase in temperature due to the increased atomic vibrations and collisions, leading to a decrease in the flow of current.

• Protection: The main function of a fuse wire is to protect the electrical circuit from overloading and short circuits. Placing it in the live wire ensures that it breaks the circuit in case of excessive current flow.



• Safety: By placing the fuse wire in the live wire, it minimizes the risk of electric shock to individuals who may come in contact with the circuit.



• Effective Functionality: The live wire is the one that carries the current into the circuit, so placing the fuse wire in this line ensures that it can effectively monitor and interrupt the flow of current when necessary.



• Standard Practice: It is a standard practice in electrical wiring to insert the fuse wire in the live wire to ensure consistent and reliable protection against electrical faults.

• Series Combination: In a series combination of electrical appliances, the appliances are connected in a line one after the other.


• Total Electrical Power: The total electrical power consumed in a series combination is equal to the sum of the individual power ratings of all the appliances.


• Decreases: When appliances are connected in series, the total resistance increases, which leads to a decrease in the total electrical power consumed.


• Ohm's Law: According to Ohm's law, power is inversely proportional to resistance. Therefore, as resistance increases in a series combination, the total power decreases.


• Example: For example, if two appliances with power ratings of 100W and 200W are connected in series, the total power consumed would be 300W (100W + 200W = 300W).

• Resistance in Parallel Combination: In a parallel combination of resistors, the total resistance is less than the smallest individual resistor in the combination.


• Area of Cross-Section: When resistors are connected in parallel, the total area of cross-section for the current flow increases. This increase in the area allows for more paths for the current to flow through, effectively reducing the overall resistance of the circuit.


• Relationship Between Resistance and Area: Resistance is inversely proportional to the area of cross-section. This means that as the area of cross-section increases, the resistance decreases.


• Impact on Resistance: As the resistance decreases in a parallel combination, the overall resistance of the circuit decreases as well. This is why resistance decreases due to an increase in the area of cross-section in a parallel combination.

• High Resistivity: Fuse wire should have high resistivity to ensure that it does not conduct current under normal conditions.


• Low Melting Point: Fuse wire should have a low melting point so that it melts quickly when there is an excessive current flow, thus breaking the circuit and preventing damage to other components.

• Fuse wire is designed to protect electrical circuits from overloads and short circuits by melting when excessive current flows through it.


• High resistivity ensures that the fuse wire does not conduct current under normal conditions, maintaining the integrity of the circuit.


• Low melting point allows the fuse wire to melt quickly when there is a surge in current, breaking the circuit and preventing further damage.


• These characteristics make fuse wire a crucial component in electrical systems to avoid damage to equipment and ensure safety.

• Initial Conditions: Two charged bodies having equal potential are connected through a conducting wire. This means that both bodies have the same amount of charge and therefore the same potential.


• Equal Potential: When two bodies have the same potential, there is no potential difference between them. As a result, no current will flow between them.


• Conducting Wire: The conducting wire simply acts as a pathway for the charges to move between the two bodies. However, since the potential is the same on both ends, there is no driving force for the charges to move.


• No Potential Difference: Current flows only when there is a potential difference between two points. In this case, since the two bodies have equal potential, there is no potential difference and therefore no current will flow.

• Voltage: Voltage is the force that pushes the electric current through a conductor. When the voltage increases, the force pushing the electrons increases, causing an increase in current.


• Current: Current is the flow of electric charge. According to Ohm's law, the current flowing through a conductor is directly proportional to the voltage applied across it. So, when the voltage increases, the current also increases.


• Resistance: Resistance is the opposition to the flow of electric current. In Ohm's law, resistance is inversely proportional to the current. This means that when the voltage increases, the current increases, which in turn increases the resistance in the circuit.

Based on the above explanation, it can be concluded that the current increases with the increases in Voltage according to Ohm's law.

• Definition of a voltmeter: A voltmeter is a device used to measure the voltage or potential difference in an electrical circuit.


• Characteristics of a voltmeter: A voltmeter is designed to have a high resistance so that it does not draw significant current from the circuit being measured. This is important to ensure accurate voltage readings.


• Connection in a circuit: A voltmeter is always connected in parallel to the component or points across which the voltage is to be measured. This is because connecting a voltmeter in series would affect the current flow in the circuit and give inaccurate readings.


• Reason for using parallel connection: When a voltmeter is connected in parallel, it has a minimal impact on the circuit's current flow due to its high resistance. This allows the voltmeter to accurately measure the voltage without affecting the overall circuit operation.


• Correct statement: Therefore, the correct statement is that a voltmeter is a high resistance instrument and is connected in parallel circuit.

• Length of conductor: The resistance of a conductor is directly proportional to its length. Longer conductors have higher resistance compared to shorter conductors.


• Area of cross-section: The resistance of a conductor is inversely proportional to the area of its cross-section. A larger cross-sectional area results in lower resistance.


• Temperature: The resistance of a conductor increases with an increase in temperature. This is known as temperature coefficient of resistance.


• Density: Density does not have a direct effect on the resistance of a conductor. It is not a factor that determines the resistance of a material.

Among the given options, density is the factor that does not affect the resistance of a conductor. The resistance of a conductor is primarily determined by its length, area of cross-section, and temperature, while density plays no role in this relationship.

• Nichrome: The most common material used for heating elements in electric heating appliances is nichrome. Nichrome is an alloy of nickel and chromium with high electrical resistance and is able to withstand high temperatures without oxidizing.



• Brass: Brass is not commonly used as a heating element material in electric heating appliances. It is mainly used in applications where corrosion resistance is needed.



• Silver: Silver is a good conductor of electricity but is too expensive to be used as a heating element material in most electric heating appliances.



• Copper: Copper is also a good conductor of electricity, but it is not suitable for heating elements in electric heating appliances as it has low resistance and would not generate enough heat.

• High electrical resistance: Nichrome has high electrical resistance, which allows it to generate heat efficiently when current passes through it.



• High temperature resistance: Nichrome can withstand high temperatures without oxidizing, making it suitable for use in electric heating appliances.



• Cost-effective: Nichrome is relatively inexpensive compared to other materials like silver, making it a cost-effective choice for heating elements.



• Durable: Nichrome is durable and long-lasting, providing a reliable heating element for electric heating appliances.

• Rheostat Function: The rheostat is a variable resistor that can be used to increase or decrease the magnitude of current flowing through a circuit.


• Increasing Current: By increasing the resistance in the circuit using the rheostat, the current flowing through the circuit will decrease.


• Decreasing Current: Conversely, by decreasing the resistance in the circuit using the rheostat, the current flowing through the circuit will increase.


• Variable Control: The rheostat provides a way to control the current in a circuit, making it a versatile component in electrical circuits.


• Application: Rheostats are commonly used in applications where variable control of current is required, such as in dimmer switches for lights or speed control for motors.

• Current distribution in parallel circuit: In a parallel circuit, the total current entering the circuit splits up and flows through each branch based on the resistance of that branch. The current through each resistor is determined by Ohm's Law (I = V/R), where V is the voltage across the resistor and R is the resistance of the resistor.


• Current is same in both resistors: Since the resistors are connected in parallel, they have the same voltage across them. This means that the current through each resistor will be different based on the resistance value, but the voltage across them will be the same.


• Voltage is same across both resistors: In a parallel circuit, the voltage across each resistor is the same as the total voltage of the circuit. This is because the voltage is constant across parallel branches in a circuit.