BlogNCERTImportant Topic of Physics: Solenoids

Important Topic of Physics: Solenoids

A solenoid is a class of electromagnets. A solenoid is an actuator unit with a moving ferromagnetic plunger inside the coil in electromagnetic technology. When the plunger is not powered, it extends outside the coil for a portion of its length; when power is applied, the plunger is pulled into the coil. Solenoids do not include electromagnets with fixed cores. To improve efficiency, it usually features a multiturn coil of magnet wire encircled by a frame that also serves as a magnetic flux carrier. A solenoid, to put it simply, turns electricity into mechanical work. The academic research concentrated on a helix, and A regulated magnetic field is generated by the helix.

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    A brief outline

    • When an electric current is delivered through the coil, it can establish a homogenous magnetic field in a region of space. In television camera tubes like vidicons and image orthicons, such solenoids offer magnetic focusing of electrons in vacuums.
    • Within the magnetic field, electrons follow helical trajectories. These focus coils, or solenoids, encircle nearly the entire length of the tube.
    • A solenoid valve, which constantly contains an electron-mechanical solenoid that agitates instead of a pneumatic or hydraulic valve, or a solenoid switch, which would be a subtype of relay that from within uses an electrical and mechanical solenoid to activate an electrical switch, including an automobile starter solenoid or linear solenoid, are also widely termed to as “solenoid.”
    • Electromechanical locking features such as solenoid bolts. Any device that uses a solenoid to transfer electrical power into mechanical power is referred to as a solenoid. The gadget uses electric current to generate a magnetic field, which is then used to create linear motion.

    A toroid is a solenoid twisted into a circular form that closes into a loop-like structure. The toroid is a hollow section ring with several turns of enameled wire tightly twisted with the negligible gap between any two turns, as depicted in the image below.

    Within and without the toroid, the magnetic field is zero. According to the right-hand thumb rule for circular loops, the magnetic field inside the toroid is constant in magnitude as well as its direction within the toroid is clockwise.

    Important concepts

    Working Principle of a Solenoid

    The solenoid operates on the basis of “electromagnetism.” When current flows through a coil, a magnetic field is formed in it; however, if a metal core is placed inside the coil, the magnetic lines of flux were focused on the core, increasing the coil’s induction over an air core. In our previous Tesla coil experiment, we expanded on the concept of electromagnetic induction. The majority of the flux is centered only on the core, with a little amount of flux appearing at the coil’s ends and outside the coil. Raise the density of the turns or enhance the current to increase the magnetic strength of the solenoid.

    The active solenoid, like all other magnets, has both Positively and Negatively poles, which can attract or repel an object. Solenoids exist in a range of shapes and sizes.

    There are various types of solenoids on the market, which are classified according to material, design, and purpose.

    • Solenoid with a DC-C Frame
    • Solenoid with a DC-D Frame
    • Laminated Solenoid (AC)
    • Solenoid Linear
    • Solenoid Rotation

    Solenoid with AC Lamination

    A metal core and a wire coil make up the AC laminated Solenoid. The core is made of laminated metal to reduce stray current and improve the solenoid’s functionality. Because it can provide a considerable degree of force in the first stroke, an AC solenoid offers a distinct advantage. This is due to the fact that they would have an inrush current. They can use a greater number of strokes than a DC laminated solenoid. Medical equipment, locks, cars, industrial equipment, printers, and some of the other items that demand immediate response can all benefit from an AC laminated solenoid.

    Solenoid for DC C-Frame

    The solenoid’s design is referred to as the C frame. The DC C-Frame solenoid comprises merely a letter C-shaped frame that is wrapped around the coil. Because of its more regulated stroke function, the DC C-Frame solenoid is being used in a variety of everyday applications. Although they are described as having a DC configuration, they could also be used in AC-powered devices. Gaming devices, photographic shutters, scans, circuit breakers, coin counters, and bill changers all use this sort of solenoid.

    Solenoid for DC D-Frame

    The coils are covered by a two-piece frame on this sort of solenoid. They perform similarly to a C-frame solenoid; therefore, the D-frame can be operated with AC power and has a regulated stroke. Gaming machines, ATM machines, and blood and gas analyzers are all examples of applications where the DC D-frame solenoid is used.

    Solenoid Linear

    People are better familiar with linear solenoids. It is made up of a coil of wire wrapped around a moveable metal core that allows us to exert pulling or pushing force on a mechanical device. This sort of solenoid is commonly used in starters. This switching device assists in the completion of a circuit by allowing current to pass through it. Linear solenoids are commonly employed in automation, highly secure door mechanisms, and vehicle and motorcycle starter motors.

    Solenoid Rotation

    A rotary solenoid is a special form of the solenoid that is utilized in a variety of applications where an easy automatic control procedure is required. It operates in the same way as other solenoids and contains the same components, such as a coil and a core, but it has a different function. The metal core is positioned on a disc with small grooves beneath it that perfectly fit the slots in the solenoid’s body. It also includes ball bearings for smooth movement. The core of the solenoid is sucked into the body of the solenoid when it is triggered, and the disc core begins to rotate.

    For control valves, electromagnetic switches, and mechanical interlocks, solenoids offer a straightforward and powerful choice. Their activity idea and fast reaction caused them a better option for applications that require an incredible amount of force in a short space and have to work rapidly, reliably, and dependably. Solenoids are utilized in both home and modern gear, and they arrive in an assortment of plans, each with its own arrangement of employment. No matter what the application, the functioning idea is similar all of the time. Profoundly, the solenoid can create an attractive field from electric flow, which can then be used to produce straight movement. In a circuit, this essential contraption can work as an electromagnet, an inductor, or a little remote getting receiving wire.

    Significance of Solenoids in NEET exam

    The study materials from Infinity Learn allow students to access resources online at their leisure and from the convenience of their own homes. It is written by subject matter specialists and is hence 100 percent accurate and dependable for tests like NEET. The study material from Infinity Learn is available for download in pdf format, which students can store for future reference or view in an online manner. The study materials assist students in quickly resolving their doubts.

    Also read: Important Topic of Physics: Superposition Principle

    Frequently asked questions (FAQs)

    Question 1: What are the Characteristics of solenoids?


    • The poles of a bar magnet are not exactly at the end of the magnet, but rather inside it. Poles in a solenoid can be thought of as lying on the edge.
    • The magnetism in the bar magnet is naturally retained, whereas the magnetism in the solenoid is retained for as long as current flows through it.
    • A bar magnet’s magnetic field extends throughout the magnet’s body, with greater intensity at the poles. While there is no field originating from the solenoid’s lateral surface.

    Question 2: Explain how a solenoid works.


    • A solenoid is a coil of wire tied across a corkscrew-shaped piston, usually made of iron.
    • When an electric current runs through the wire, a magnetic field is created, as it is with all electromagnets.
    • Electromagnets have the benefit over permanent magnetic materials in that they can be turned on and off by changing the electrical field, making them useful as controllers and switches that can be automated.
    • The positive and negative poles of an operational solenoid’s magnetic field attract or repel sensitive material from the magnets.
    • The electrical force forces the piston within a solenoid to shift forward or backward, which is how motion is created.

    Question 3: What Does the Magnetic Field Inside a Solenoid Look Like?

    Answer: The magnetic field from the inside of a solenoid has always been uniform, which means it has the same magnetic force across the coil.

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