# 28 Lecture

## Currents and Circuits

Currents and circuits are fundamental concepts in the study of physics. Current refers to the flow of charged particles, such as electrons, in a conductor. Circuits, on the other hand, refer to the paths that these charged particles take through

## Important Mcq's Midterm & Finalterm Prepration Past papers included

In a simple circuit consisting of a resistor and a battery, what happens to the current if the resistance is doubled?

a) The current doubles

b) The current is halved

c) The current remains the same

d) The current becomes zero

Answer: b) The current is halved

What is the unit of electric current?

a) Joule

b) Coulomb

c) Watt

d) Ampere

In a parallel circuit, what happens to the total resistance when additional resistors are added?

a) The total resistance decreases

b) The total resistance increases

c) The total resistance remains the same

d) The total resistance becomes zero

Answer: a) The total resistance decreases

What is the relationship between voltage, current, and resistance in a circuit?

a) V = IR

b) I = VR

c) R = IV

d) V = RI

In a circuit with a battery and a single resistor, what happens to the current if the voltage of the battery is increased?

a) The current increases

b) The current decreases

c) The current remains the same

d) The current becomes zero

What is the role of a capacitor in a circuit?

a) To store energy in the form of electric charge

b) To increase the resistance of the circuit

c) To reduce the resistance of the circuit

d) To act as a switch

Answer: a) To store energy in the form of electric charge

In a circuit with multiple resistors in series, what happens to the total resistance when the resistors are replaced with ones of lower resistance?

a) The total resistance increases

b) The total resistance decreases

c) The total resistance remains the same

d) The total resistance becomes zero

Answer: b) The total resistance decreases

What is the unit of electric potential difference?

a) Volt

b) Joule

c) Coulomb

d) Watt

In a series circuit, what happens to the current as it passes through each component?

a) The current increases

b) The current decreases

c) The current remains the same

d) The current becomes zero

What is the relationship between power, voltage, and current in a circuit?

a) P = VI

b) V = PI

c) I = PV

d) P = IV

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is an electric current, and what are its units?

Answer: Electric current is the flow of electric charges through a conductor. It is measured in amperes (A).

What is Ohm’s Law, and how is it used in circuits?

Answer: Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to its resistance. It is commonly used to calculate the resistance, current or voltage of a circuit.

What is the difference between AC and DC current?

Answer: AC (alternating current) changes direction periodically, while DC (direct current) flows in only one direction.

What is a circuit diagram, and how is it useful?

Answer: A circuit diagram is a graphical representation of an electrical circuit that shows how the various components are connected. It is useful for understanding the functioning of the circuit and troubleshooting it if any problem arises.

What is a series circuit, and how does it differ from a parallel circuit?

Answer: In a series circuit, the components are connected in a single loop, while in a parallel circuit, the components are connected in separate branches.

What is a resistor, and how does it affect the flow of current in a circuit?

Answer: A resistor is an electrical component that resists the flow of current in a circuit. It is used to regulate the amount of current flowing through a circuit.

What is a capacitor, and how is it used in a circuit?

Answer: A capacitor is an electrical component that stores electric charge. It is commonly used in circuits to block DC current and pass AC current.

What is an inductor, and how does it affect the flow of current in a circuit?

Answer: An inductor is an electrical component that stores energy in a magnetic field. It is used to oppose changes in current flow in a circuit.

What is a diode, and what is its purpose in a circuit?

Answer: A diode is an electrical component that allows current to flow in only one direction. It is used to regulate the flow of current in a circuit and prevent reverse current.

What is a transistor, and how is it used in electronic devices?

Answer: A transistor is an electrical component that is used to amplify or switch electronic signals. It is a fundamental building block of modern electronic devices such as computers and smartphones.

### Currents and Circuits

Currents and circuits are fundamental concepts in the study of physics. Current refers to the flow of charged particles, such as electrons, in a conductor. Circuits, on the other hand, refer to the paths that these charged particles take through a series of components, such as resistors, capacitors, and inductors, that are connected by wires. Understanding currents and circuits is crucial for understanding how electricity works and how it can be applied in various devices and technologies. One important concept related to currents and circuits is the idea of electric potential difference, which is the difference in electric potential energy per unit charge between two points in a circuit. This potential difference, measured in volts, drives the flow of charge through a circuit. In a simple circuit, the potential difference is provided by a battery or other source of electrical energy, which sets up an electric field that drives the flow of electrons through the circuit. Another important concept in circuits is resistance, which refers to the property of a material that impedes the flow of current through it. Resistance is measured in ohms and is represented by the symbol ?. The resistance of a material depends on various factors, such as its temperature, the material's composition, and the shape and size of the material. Circuits can be connected in series or parallel configurations. In a series circuit, components are connected one after the other in a single path. The current through each component in a series circuit is the same, but the potential difference across each component can be different. In a parallel circuit, components are connected in multiple paths, so the potential difference across each component is the same, but the current through each component can be different. Another important concept related to circuits is the idea of capacitance, which is the ability of a material to store electrical charge. A capacitor is a device that stores electrical energy in an electric field. Capacitance is measured in farads, and it depends on various factors, such as the distance between the plates of the capacitor, the area of the plates, and the material between the plates. The flow of current through a circuit can also produce a magnetic field. This is known as electromagnetic induction, and it is the basis for many devices, such as transformers and electric generators. In an electric generator, a magnetic field is used to induce a current in a wire, producing electrical energy. In a transformer, a changing magnetic field is used to induce a current in a nearby wire, allowing the electrical energy to be transferred from one circuit to another. Finally, circuits can be analyzed using Kirchhoff's laws, which are a set of rules that govern the behavior of currents and voltages in a circuit. Kirchhoff's laws state that the sum of the currents entering a node in a circuit must equal the sum of the currents leaving the node, and the sum of the potential differences around any closed loop in a circuit must be zero. In conclusion, currents and circuits are important concepts in the study of physics, and they are essential for understanding how electricity works and how it can be applied in various devices and technologies. By understanding the basic principles of electric potential difference, resistance, capacitance, and electromagnetic induction, and applying Kirchhoff's laws, physicists can design and build complex circuits that are used in many areas of technology and industry.