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Physics Chemistry ⋅ Biology Technics  LEYBOLD DIDACTIC GMBH

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Instruction Sheet 521 11

1 Safety notes 2 Description

The induction coil for 10 cm spark length has a primary windingof 250 turns and a secondary winding of 26,000 turns. The devi-ce contains a contact breaker. The induction coil requires about8 V DC and consumes 4 to 5 A in operation and up to 10 A whenno load is connected. The current is supplied via a commutator

mounted on the base plate, which also serves as a switch. Theinduced high voltage is present between a plate electrode and aneedle electrode which can be moved to vary the distance. Thevoltage can be tapped via 4-mm sockets.

3 Putting into operation (see Fig. 1):

Important: rocker stator D of the contact breakers was alreadyset in the optimum position before the device was shipped(distance to metal body E!). Do not manipulate any of the variousscrews, except for the contact screws (A and B).

First make sure that contacts (G) of the contact breaker are justtouching. To set these, first loosen the large screw (A), set thecontact in the desired position with screw (B) and then retightenscrew (A).

Connect the voltage to the two terminals next to the commuta-tor. Reliable contact is ensured when the commutator is in thehorizontal position. After switching on, push rocker stator D. Ifthe induction coil does not respond, readjust the contact withscrew (B).

When the experiment is over, switch off the voltage or set thecommutator in the vertical position so that no current can flowthrough the deactivated induction coil.

If the factory-set adjustment of the device is changed, you willneed to reset the contact breaker. Set the distance of the entirecontact breaker to the coil by loosening the two screws on thebase plate. The two iron bodies (E) should be spaced about5 mm apart; if this spacing is too small the moving part (D) willbecome caught.

Set the opening speed with screw (C), which is secured by aknurled nut. Loosen screw (C) to obtain the greatest possibleopening speed. However, if you turn this screw too far, the in-duction coil does not function. Carry out all these steps aftersetting screw (B) in the optimum position.

Induction Coil, 10 cm Spark Length

Fig. 1

• Contact-hazardous high voltage! 

This device supplies a high voltage which may represent acontact hazard, depending on how the device parametershave been configured.

- This device may be put into operation by the subjectteacher only.

- This device may only be operated by the subject teacheror another person who has been instructed and isknowledgeable in the dangers of contact-hazardous highvoltage.

- Set up and configure the device only when the supply volt-age is switched off.

- Do not touch the metal parts of the device during opera-tion;make sure that it is not possible for anyone to inadvertentlytouch metal parts.

- Do not exceed the maximum permissible supply voltage of

8 V DC.• X-ray regulations.

In the Federal Republic of Germany, it is not permitted tooperate vacuum or discharge tubes with the induction coil,due to the applicable x-ray regulations.Be sure to observe all regulations which apply in your country.

• Electromagnetic compatibility (EMC)

This device can cause radio interference in a range of up to500 m; the operator may be required to implement appro-priate measures and to bear the costs for these.For brief operation (a few seconds), it may be assumed thatno impermissible radio interference can occur.

To further reduce possible radio interference:keep the connecting leads between the power supply and

the induction coil as short as possible.

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LEYBOLD DIDACTIC GMBH ⋅ Leyboldstrasse 1 ⋅ D-50354 Hürth ⋅ Phone (02233) 604-0 ⋅ Telefax (02233) 604-222 ⋅ e-mail: info@leybold-didactic.de © by Leybold Didactic GmbH Printed in the Federal Republic of Germany

Technical alterations reserved

You can change the contact setting with screw (F). However,you should leave this screw as loose as possible, as carelesstightening can easily damage the contact breaker.

After long operation, the contacts may wear down unevenly,and their surface become altered. This reduces the power ofthe induction coil. In this case, file the faces of the contacts flatusing a small file.

4 Determining the polarity

When the induction coil is in operation, turn contact screw (B)until you find the position with the greatest spark discharge.

Then turn the commutator by 180°. If the flashover distance isnow greater, do not change this commutator position; otherwisereturn to the original position. The induction coil now has the“right” polarity, i.e. the needle is the positive pole and the plateis the negative pole.