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What is the total of the numbers on a clock face?

The sum of all the numbers is 78.

Why do clocks have a face?

Clocks can indicate the hour with Roman numerals or Hindu–Arabic numerals, or with non-numeric indicator marks. Clocks using only Arabic numerals first began to appear in the mid-18th century. The periphery of a clock’s face, where the numbers and other graduations appear, is often called the chapter ring.

Who invented clock face?

Ibn al-Haytham’s

What is clock face rule?

Here, the clock rule says that “When an observer, looking at the face of the coil, finds the current to be flowing in the anti-clockwise direction, here the face of the coil will behave like a North Pole, whereas if the current is in the clockwise direction, the face of the coil will behave like a South Pole.”

What is Snow rule?

SNOW rules state that if the current is flowing in an electric circuit from South to North direction and the magnetic compass is placed Over the conducting wire, the needle of the compass deflects in the West direction.

What is the face of a coil?

C) Anti-clockwise direction and this face represents the north pole. D) Clockwise direction and this face represents the south pole. Answer Verified. Hint: We know that the current in an induced coil follows a definite direction and produces magnetic dipoles according to its movement.

How can you reverse the polarity of an electromagnet?

Reversing The Polarity Of an Electromagnet:

  1. Determine the poles of the magnet and mark them accordingly (N=North, S=South)
  2. Turn off the power switch.
  3. Use a tool (pliers/screwdriver) to disconnect the two wires.
  4. Switch the positions of the wires.
  5. Turn the power back on and test the polarity.

Can the polarity of a permanent magnet be reversed?

The easiest way to reverse the poles of a permanent magnet is to simply physically turn the magnet around 180 degrees.

Can we change the polarity of a permanent magnet?

The (north-south) polarity of a permanent magnet is fixed and cannot be changed. 4. The polarity of an electromagnet can be changed by changing the direction of current in its coil.

What are 3 parts of an electromagnet?

There are three main parts required to build an electromagnet: the iron core, copper wire, and an electricity source.

Which one is not part of electromagnet?

Answer: Wire,iron, and toothpick. Explanation: It is not the part of an electromagnet.

What is an electromagnet Class 7?

Answer: An electromagnet is a coil of insulated wire wound around a piece of a magnetic substance such as soft iron. The magnetic substance acts as a magnet as long as the current flows in the wire.

What is electromagnet very short answer?

An electromagnet is a temporary magnet which behaves like a magnet when an electric current is passed through the insulated copper wire and loses its magnetism when current is stopped. It has a soft iron piece called the core with an insulated copper wire wound on it.

What is an electric fuse Class 7?

An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it. It is made of a special material. As the current increases beyond a limit, the wire in the electric fuse melts and breaks off.

What are the causes of fire in electric circuit class 7?


  • faulty outlets,appliances.
  • light fixtures .
  • Extension cords.
  • Space heaters.
  • Wiring.

What is an electric fuse short answer?

In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current.

What size fuses are there?

Size groups

Blade size Blade group Common ratings (maximum current)
LP-Mini (low profile) APS, ATT 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30
Mini APM, ATM 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30
Regular APR, ATC, ATO, ATS 0.5, 1, 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30, 35, 40
Maxi APX 20, 25, 30, 35, 40, 50, 60, 70, 80, 100, 120

What is a Class K fuse?

Class K fuses. These non-renewable fuses are available in 250VAC and 600VAC ratings, with current ratings from 0A to 600A. Class K fuses are available with DC ratings. The interrupting ratings may be 50kA, 100kA, or 200kA rms symmetrical. Class K-1 fuses provide the best degree of current limitation.