50 questions · timed · auto-graded
It deflects a magnetic needle placed near it because a magnetic field is created when the current passes through it.
In a buzzer, the simplest sort of doorbell, an electromagnet is used to operate a self - interrupting circuit.
You can see how this system works in the diagram below.
Click and hold the doorbell button to see how the buzzer works.
This breaks the doorbell circuit, which shuts off the electromagnet.characteristic of a buzzer It has higher frequency of collision of gong and hammer.
The working of an electric magnet is based on the magnetic effect of the current.
When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature.
This movement of the armature causes the hammer to strike the gong.
However, when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit, and the current flow is stopped thus demagnetizing the electromagnet.
This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip.
This process is called a make and brake circuit.
Always fuse breaks on shorting of wire and flowing exessive current.
Because of lack of flexibility, striker will resist change of motion more and may break if current is large.
Without flexibility, no rebounding force is present and striker will not return to its original position.
Most heating elements use Nichrome $ \frac{80}{20}$ $(80\%$ nickel, $20\%$ chromium$)$ wire, ribbon, or strip.
Nichrome $ \frac{80}{20}$ is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time.
Material beneath this layer will not oxidize, preventing the wire from breaking or burning out.Hence, nichrome is used as heating elements.
Ammeter measures current.
When the switch is off, the circuit is in open position and current does not flow through the circuit as the circuit is not complete.
So, the correct options are $(ii), (iii).$
Switches allow the user of gadget to turn off the gadget when not required. Hence, $A$ and $C$ follows.
Using a device only when required reduced the wear and tear and protects the system.
The given symbol is the symbol of the Electric bulb used in a circuit diagram.
For using electric gadgets/ appliances/ circuit, we have to turn the switch in $ON$ position. Therefore, precaution given in option $(d)$ need not be considered.
These days $MCBs$ (miniature circuit breakers) are used in place of electric fuses.
They are switches which turn off automatically when current exceeds safe limit.
$\text{ESSENTIAL REQUIREMENTS OF GOOD HEATING ELEMENT}$ High-specific resistance so that small length of wire may be required to provide given amount of heat.
High - melting point so that it can withstand for high temperature, a small increase in temperature will not destroy the element.
When the switch is in $OFF$ position, circuit is incomplete. It is said to be open and therefore, no current flows through it.