Physics: Practice Questions On Electric Currents And Force!

A current that flows in just one direction is known as direct current. Direct current (DC) is the flow of electric charge in a constant direction, typically generated by batteries or power supplies. Unlike alternating current (AC), which periodically changes direction, direct current maintains a steady flow of electrons in a single direction. DC is commonly used in electronics, such as powering electronic devices and charging batteries.

The given statement explains that one coulomb of negative charge is equivalent to the charge carried by 6.25 * 10^18 electrons. This means that if we have a total of 6.25 * 10^18 electrons, their combined charge would be equal to one coulomb. The coulomb is the unit of electric charge in the International System of Units (SI).

The speed of electrons due to the current is called their drift velocity. This term refers to the average velocity at which electrons move in a conductor when an electric field is applied. It is important to note that the drift velocity is much slower compared to the speed of individual electrons. The drift velocity is influenced by factors such as the magnitude of the electric field, the density of free electrons in the conductor, and the cross-sectional area of the conductor.

A device with constant resistance is known as a resistor. A resistor is an electronic component that restricts the flow of electric current in a circuit. It is designed to have a specific resistance value, which remains constant regardless of the voltage or current passing through it. Resistor is a fundamental component used in various electrical and electronic systems to control the flow of electricity and to provide stability and protection to other components in the circuit.

The explanation for the given correct answer is that a circuit refers to the complete path that the moving charges, or current, follows. It includes all the components such as wires, resistors, capacitors, and other electrical devices that are connected together to form a closed loop. The circuit allows the flow of electric current from the power source to the load and back to the source, enabling the transfer of energy and the operation of electrical devices.

A potentiometer is a variable potential divider that is used to divide up the potential difference of a battery. It consists of two resistors that can be adjusted to vary the output voltage. By changing the position of the sliding contact, the resistance ratio between the two resistors can be changed, thereby changing the output voltage. This allows for precise control and measurement of voltage in various electrical circuits. Therefore, a variable potential divider is commonly known as a potentiometer.

Newton's theory of universal gravitation states that every mass in the Universe attracts all other masses in the Universe. This means that any two objects with mass will exert a gravitational force on each other. The strength of this force depends on the masses of the objects and the distance between them. This theory explains why objects fall to the ground, why planets orbit the Sun, and why galaxies are held together. It is a fundamental concept in physics and has been widely accepted since its formulation by Sir Isaac Newton in the 17th century.

Matter that contains no charge, or equal amounts of positive and negative charge, is said to be electrically neutral. This means that the total positive charge of the matter is equal to the total negative charge, resulting in a net charge of zero. In other words, there is a balance between positive and negative charges, making the matter neither positively nor negatively charged.

(B) defines an insulator.

The force that exists between all charges is known as the electrostatic force. This force is responsible for the interaction between electrically charged particles, such as protons and electrons. It is a fundamental force in nature and plays a crucial role in many phenomena, including the behavior of atoms, the flow of electricity, and the formation of lightning. The electrostatic force can be attractive or repulsive, depending on the charges involved and their distances from each other. It is described by Coulomb's law, which states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

The rate of flow of electrical charge is defined as current. Current refers to the flow of electric charge in a circuit or conductor. It is measured in amperes (A) and is essential for the functioning of electrical devices.

An alternating current is a type of current that constantly changes direction. Unlike direct current, which flows in only one direction, alternating current periodically reverses direction. This is achieved through the use of an alternating voltage source, such as an AC generator. Alternating current is commonly used in homes and businesses for powering electrical devices, as it can be easily transmitted over long distances and efficiently transformed into different voltage levels.

The electromotive force (e.m.f.) is the total energy difference per unit charge around a circuit. It represents the potential difference or voltage that drives the flow of electric current in a circuit. The e.m.f. is responsible for creating an electric field that pushes the charges and maintains the current flow. It is measured in volts and is independent of the circuit's internal resistance.

A parallel circuit is branched as such. A series circuit, however, has components conected one after another in a continuous chain.

A perfect ammeter has zero resistance (a perfect voltmeter has infinite resistance)

A thermistor is a type of resistor whose resistance changes with temperature. It is designed to have a high sensitivity to temperature variations, making it useful in applications where temperature monitoring or control is required. The resistance of a thermistor decreases as the temperature increases, and vice versa. This characteristic allows thermistors to be used in temperature sensing and compensation circuits, as well as in temperature control systems. Therefore, a resistor whose value of resistance depends on its temperature is known as a thermistor.

A conventional current flows from positive to negative because it is based on the historical convention established before the discovery of electrons. This convention assumes that current flows from the positive terminal of a power source to the negative terminal. However, in reality, electrons flow in the opposite direction, from negative to positive. Nonetheless, the conventional current flow is still widely used in circuit analysis and electrical engineering.

Electric field is the force per unit charge on a positive test charge

(A) defines a light dependent resistor (LDR). (C) defines a thermistor. (D) defines a sensor circuit

It is the energy difference per unit charge moved.

According to Ohm's law, the current flowing through a piece of metal is proportional to the potential difference across it, if the temperature is constant. This means that as long as the temperature remains the same, the current will increase or decrease in direct proportion to the potential difference. The other factors mentioned (resistance, pressure, and cross-sectional area) may also affect the current, but they are not mentioned in the question as being constant. Therefore, the correct answer is that the temperature must be constant for Ohm's law to hold true.

The lines of a magnetic field are also called flux lines. This term is commonly used to describe the visual representation of the magnetic field, showing the direction and strength of the field at different points. These lines help us understand the behavior and properties of magnetic fields and are used in various applications, such as in magnetic field mapping and analysis.

The correct answer is Motor effect. The explanation for this is that when a current-carrying wire is placed in a magnetic field, the interaction between the magnetic field and the current in the wire creates a force. This force is known as the motor effect and is the basis for the operation of electric motors.