Test: Current Electricity - Class 9 MCQ

In a parallel circuit, the total current divides among the different branches, allowing each component to operate independently. This means each component can have a different current depending on its resistance.

Ohm's law states that the voltage (V) across a conductor is equal to the current (I) flowing through it multiplied by the resistance (R) of the conductor, expressed as \( V = I \times R \).

A lead-acid battery is a common example of a secondary cell, known for its ability to be recharged multiple times through reversible chemical reactions, making it suitable for long-term use in applications like car batteries.

Potential difference (voltage) is significant because it creates the necessary force to drive electric charge through a circuit, enabling current to flow and power electrical devices.

When a positively charged conductor is connected to an uncharged conductor, electrons flow from the uncharged conductor to the charged one to balance the charge difference, resulting in both conductors having a neutral charge.

A rheostat is used to control the amount of current flowing in a circuit by varying the resistance. This is useful for adjusting the brightness of bulbs or the speed of motors.

Primary cells produce current through irreversible chemical reactions and are designed to be used once before disposal. Examples include dry cells and Leclanche cells.

Compact fluorescent lights (CFL) contribute to energy efficiency by using significantly less energy than incandescent bulbs while providing the same amount of light, thereby reducing overall energy consumption.

A voltmeter is used to measure the potential difference (voltage) between two points in a circuit. It is connected in parallel to provide accurate voltage readings without significantly affecting the circuit.

The unit of electrical resistance is the ohm (Ω). It quantifies how much a material opposes the flow of electric current, with one ohm defined as the resistance when one volt causes one ampere to flow.

An ammeter measures the current flowing through a circuit. It must be connected in series to ensure that the entire current passes through it, allowing for accurate readings.

A galvanometer detects the presence and direction of current in a circuit. It does not measure the magnitude but indicates whether current is flowing and in which direction, useful for troubleshooting circuits.

Higher temperatures typically increase the resistance in a conductor due to increased vibrations of atoms, which leads to more collisions among moving electrons, impeding current flow.

Good conductors of electricity, such as copper and aluminum, have many free electrons that facilitate easy current flow. This allows them to efficiently carry electrical charge in circuits.

In a closed circuit, there is a complete path for current to flow, allowing electrical devices like bulbs to operate. If the circuit is open, current cannot flow, and devices will not function.

Implementing energy-efficient technologies significantly reduces greenhouse gas emissions by lowering energy consumption. For example, improved insulation and energy-efficient appliances can collectively cut energy needs and decrease environmental impact.

Cells supply direct current (d.c.), which flows steadily in one direction. This is crucial for devices like torches, where a consistent power source is needed to light the bulb.

This formula defines electric current (I) as the rate of flow of electric charge (Q) over time (t). It highlights how current is measured in amperes, where one ampere equals one coulomb per second.

Insulators, such as rubber and plastic, have high resistance and do not allow current to flow easily, while conductors, like metals, have low resistance and facilitate the easy flow of electrical current.

LED bulbs are more energy-efficient and have a longer lifespan compared to incandescent bulbs, using significantly less energy for the same amount of light output, making them a better choice for reducing energy consumption.