Dry Cell



Dry cell

A dry cell is an electrochemical cell that uses a low-moisture electrolyte instead of a liquid electrolyte as a wet cell does. This feature makes the dry cell much less prone to leaking and is therefore more suitable for portable applications. The zinc-carbon battery is one of the most common examples of a dry cell battery.

Carbon Rod

The center of a zinc-carbon battery is a rod of pure carbon in the form of graphite. The carbon rod is covered in a mixture of carbon powder and manganese dioxide. It’s important to note that the carbon won’t play any role in the electrochemical reaction that will produce the current. The purpose of the carbon rod is simply to allow the flow of electrons. The carbon powder will increase the electrical conductivity of the Mn02 and retain the moisture of the electrolyte.

Electrolyte

The carbon rod is surrounded by an electrolytic paste of ammonium chloride and zinc chloride. This paste is not completely dry, since some liquid is needed for the chemical reactions to occur readily. The ammonium ion will react with the manganese dioxide to carry electrons to the carbon rod. This reaction will produce dimanganese trioxide, water and ammonia as byproducts.

Zinc Sleeve

The electrolytic paste is encased in a sleeve of zinc metal. The zinc metal will oxidize, causing it to donate two electrons for each zinc atom. These electrons will flow through the electrolyte into the carbon rod to produce an electrical current. This sleeve will get thinner as the zinc oxidizes and the battery will no longer be able to conduct electricity once the zinc sleeve is completely gone.

Additional Components

The top of the battery is covered by a conductive plate so that the carbon rod can make contact with the positive terminal on the outside of the battery. A non-conductive tube forms the sides of the battery and ensures that there is no direct electrical contact between the carbon rod and the zinc sleeve.

Operation

The electrons flow from the zinc sleeve to the carbon rod, so the zinc sleeve is the anode and the carbon rod is the cathode. This type of dry cell initially produces about 1.5 volts, which decreases as the battery is used. It deteriorates rapidly in cold weather and will begin leaking its contents — primarily ammonium chloride –when the zinc sleeve is consumed.

Accumulator cell

An accumulator is an energy storage device: a device which accepts energy, stores energy, and releases energy as needed. Some accumulators accept energy at a low rate (low power) over a long time interval and deliver the energy at a high rate (high power) over a short time interval. Some accumulators accept energy at a high rate over a short time interval and deliver the energy at a low rate over longer time interval. Some accumulators typically accept and release energy at comparable rates. Various devices can store thermal energy, mechanical energy, and electrical energy. Energy is usually accepted and delivered in the same form. Some devices store a different form of energy than what they receive and deliver performing energy conversion on the way in and on the way out.  

Examples of accumulators include steam accumulators, mainsprings, flywheel energy storage, hydraulic accumulators, rechargeable batteries, capacitors, compensated pulsed alternators (compulsators), and pumped-storage hydroelectric plants.

Magnetic effect of current

Magnetic effect of electric current is one of the major effects which functions as the basic principle in appliances used in various fields of activities. The magnetic field around a current carrying conductor can be depicted by using magnetic field lines which are represented in the form of concentric circles around it. The direction of magnetic field through a current carrying conductor is determined by the direction of flow of electric current.

Magnetic effect of electric current is one of the major effects which functions as the basic principle in appliances used in various fields of activities. The magnetic field around a current carrying conductor can be depicted by using magnetic field lines which are represented in the form of concentric circles around it. The direction of magnetic field through a current carrying conductor is determined by the direction of flow of electric current.

The Right Hand Thumb Rule also known as Maxwell’s Corkscrew Rule is known to determine the direction of magnetic field in relation to direction of electric current through a straight conductor. As the direction of the electric current changes, the direction of the magnetic field also gets reversed. If the direction of electric current in a vertically suspended current carrying conductor is from south to north, the magnetic field will be in the anticlockwise direction. If the current is flowing from north to south, the direction of magnetic field will be clockwise. If a current carrying conductor is held by right hand; keeping the thumb straight and if the direction of electric current is in the direction of thumb, then the direction of folding of other fingers will show the direction of magnetic field. Magnitude of magnetic field is directly proportional to the number of turns of coil. If there are ‘n’ turns of coil, magnitude of magnetic field will be ‘n’ times of magnetic field in case of a single turn of coil.

Oersted’s Experiment

Hans Christian Oersted was a Danish scientist who explored the relationship between electric current and magnetism. Current is the flow of electrons, and is how we hardness electricity. Currents create their own magnetic fields in closed loops, which magnets are known to induce, or create current, in wires.  

Oersted experimented with this, using a compass, which uses the magnetic poles of the Earth to show your which direction you are facing. By bringing the compass near a closed current loop, he was able to interfere with the magnetic field and cause the compass needle to move.

Procedure

  • Cut a 1 meter loop of insulated wire.
  • Use electrical tape to secure a stripped end of the wire to one side of a D battery.
  • Run the wire up one side of the box, across the top, and down the other side. Make sure you have enough wire so that itcan run along the table or ground to reconnect the battery. Now you have a loop.
  • Connect the other open end of the wire to the battery so current begins to flow.
  • Bring the compass into the center of the loop.
  • Move the compass around closer to the wire and away from the wire. Record your observations.

Observation and result

The wire will carry a current that creates a magnetic field around itself. Bringing the compass near the wire or in the loop will cause the compass needle to move.  

The current will induce a magnetic field based on the right-handrule. Make a “thumbs-up” sign with your right hand. The thumb will be the direction of the current (flowing from the negative to positive terminal of the battery) and the fingers will curve around in the direction of the magnetic field.  The magnetic field created by the current will interfere with the magnetic field the compass experiences when it is brought near enough.


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