01․ _______________ is not an applictaion of dielectric heat.
Soldering at high temperatures or brazzing where silver, copper, their, alloys arc used as solders is another important industruial application. Two pieces of metal arc firred properly and suitable flux is applied to the joint and the soldering alloy is placed near the joint. By induction heating heat develops very rapidly melting the solder which runs into the joint sealing it properly.
02․ Low frequency supply is necessary for direct core type induction furnaces because
Low frequency supply is necessary for direct core type induction furnace. If normal frequeny supply is employed for operation of such furnaces the electromagnetic forces cause severe stirring action in the molten metal. Hence low frequency supply is also necessary from this point of view. If magnetic coupling between the primary and secondary circuit is poor, therefore leakage reactance is high and power factor is low.
03․ For intermittent work which of the following furnace is suitable?
In indirect arc furnace, the arc is produced between two electrodes and heat is transferred to the charge by radiation only. Direct arc furnace is more suitable in situation where the charge has to be varied frequently or where heating intermitternt.
04․ The dielectric loss in a dielectric is proportional to
Dielectric loss in a dielectric is given as From above equation, P ∝ V2. Hence, we can say that dielectric loss proportional to the square of the voltage impressed on the dielectric.
05․ The power factor will be leading in case of
In dielectric heating, the current is drawn by the capacitor. When an AC supply voltage is applied across the capacitor plates, the current does lead the supply voltage by exactly 90° and there is always an in-phase component of the current. Since the dielectric heating is involved the capacitor , So the power factor will be leading in the case of dielectric heating. The value of power factor for a particular non-conducting material is constant.
06․ For dielectric heating the range of frequency normally employed is
In dielectric heating, for producing sufficient heat frequency is used between 10 MHz and 30 MHz. Dielectric heating depend upon the value of frequency. Hence to achieve more heat, high frequency is used.
07․ The metod of heating used for non conducting materials is
When non conducting parts such as wood, plastics, bones are subjected to dielectric heating, an alternative electrostatic field dielectric loss occurs. In dielectric heating use of these losses is made.
08․ The advantage(s) of eddy current heating is/are
The advantages of eddy current heating are
- It is quick, clean and convenient method.
- The control of temperature is very easy.
- The heat can made to penetrate into the metal surface to any desired depth.
- The area of surface over which heat is produced can be accurately controlled.
- It can easily take place in vacuum or any other special atmosphere. There is little wastage of heat, as heat is produced in the body to be heated up directly.
09․ The method appropriate for heating of non ferrous materials is
Due to indirect arc heating, a furnace becomes suitable for comparatively low melting point. So these furnaces are used for melting non ferrous metal.
10․ Hysteresis loss and eddy current loss arc used in
Hysteresis loss and eddy current loss arc used in induction heating of ferromagnetic materials.