Test: Electricity: Magnetic and Heating Effects - Class 8 MCQ

Thinner and longer wires generally heat up more due to higher resistance compared to thicker wires. The resistance in a conductor leads to energy loss as heat, demonstrating the importance of wire properties in electrical applications.

Electric room heaters utilize the heating effect of electric current by converting electrical energy to heat through resistance in the heating element. This principle is widely applied in various heating devices.

The dry cell is the most commonly used battery in everyday devices such as torches and TV remotes. It contains a moist paste as an electrolyte and is typically non-rechargeable, requiring disposal after use.

Rechargeable batteries can be reused multiple times, making them more cost-effective and environmentally friendly compared to single-use batteries. Examples include lithium-ion batteries used in various electronic devices.

Reversing the direction of the current flowing through an electromagnet reverses its polarity. This characteristic is essential for applications like electric motors and relays.

A simple electric cell can be made at home using a lemon, a copper strip, and an iron nail, where the lemon juice acts as an electrolyte. This setup allows the chemical reaction to generate a small electric current.

Resistance is a property of materials that opposes the flow of electric current, leading to energy loss in the form of heat. Different materials have varying resistance levels; for example, nichrome wire has a higher resistance than copper.

Hans Christian Oersted discovered that electric current creates a magnetic field in 1820. His findings were pivotal in establishing the connection between electricity and magnetism, leading to the development of electromagnetic theory.

In a dry cell, the zinc container serves as the negative terminal. It is surrounded by a moist paste that acts as the electrolyte, allowing the chemical reactions necessary for generating electricity to occur.

An electric cell generates electricity through chemical reactions occurring within it. It has two terminals, and when connected in a circuit, it allows electric current to flow.

The electrolyte in a battery facilitates chemical reactions between the electrodes, allowing the flow of ions which generates electric current. It is crucial for the battery's ability to produce electricity.

The heating effect of electric current refers to the warmth generated when current flows through a conductor, due to the resistance the material offers. This effect is utilized in various heating appliances, such as toasters and irons.

When current flows through a wire, it produces a magnetic field that causes the compass needle to deflect. This demonstration is often used to illustrate the magnetic effect of electric current.

A significant disadvantage of the heating effect of electric current is that it can lead to energy loss and overheating of wires or devices, which may cause damage, melting, or even fires if not managed properly.

The Earth's magnetic field plays a crucial role in shielding life on Earth from harmful cosmic particles and radiation from space. It also assists migratory animals in navigation, highlighting the importance of magnetism in nature.

Electric current flowing through a conductor generates a magnetic field around it. This phenomenon is fundamental in electromagnetism and is utilized in various applications, such as electric motors and transformers.

Lifting electromagnets are used in industrial settings, such as scrap yards and factories, to lift and move heavy metal objects efficiently. They can be turned on and off by controlling the electric current.

The magnetic field of an electromagnet disappears when the electric current is turned off. This characteristic allows electromagnets to be used in various applications where magnetism is needed only temporarily.

Nichrome, an alloy of nickel and chromium, is commonly used for heating elements in appliances because of its high resistance and ability to withstand high temperatures without melting.

The strength of an electromagnet increases with more turns of wire in the coil, greater current, and the use of an iron core. These factors enhance the magnetic field produced by the coil.