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School Instrument India is leading Compasses and Components Manufacturer,and supplier and Exporter in India, Algeria (Algiers), Angola (Luanda), Argentina (Buenos Aires), Armenia (Yerevan), Australia(Canberra), Austria (Vienna), Bahrain (Manama), Bangladesh (Dhaka), Bhutan (Thimphu), Bolivia (Sucre), Botswana (Gaborone), Brazil (Brasília), Brunei (Bandar Seri Begawan), Montenegro (Podgorica), Morocco (Rabat), Mozambique (Maputo), Myanmar (Naypyidaw), Namibia (Windhoek), Nepal (Kathmandu), New Zealand (Wellington), Nigeria (Abuja), Oman (Muscat), Palestine (Ramallah), Panama (Panama City), Papua New Guinea (Port Moresby), Paraguay (Asunción), Peru (Lima), Philippines (Manila)¸ Portugal (Lisbon), Qatar (Doha), Rwanda (Kigali), Saudi Arabia (Riyadh), Senegal (Dakar), Serbia (Belgrade), Sierra Leone (Freetown), Slovakia (Bratislava), South Africa (Cape Town) (Pretoria) (Bloemfontein), South Sudan (Juba), Spain (Madrid), Sri Lanka (Sri Jayawardenepura Kotte) (Colombo), Sudan (Khartoum), Syria (Damascus), Tanzania (Dodoma), Thailand (Bangkok), Togo (Lomé), Tonga (Nuku'alofa), Trinidad and Tobago (Port of Spain), Tunisia (Tunis), Turkey (Ankara), Turkmenistan (Ashgabat), Uganda (Kampala), United Arab Emirates (Abu Dhabi), United Kingdom (London), United States (Washington, D.C.)

Written by Palak Mall, Senior Content Writer · reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory supply · updated 17 October 2026

Compasses and Components holds 36 items for wiring and controlling circuits in a school or college physics lab, including two compasses: plugs, sockets and clips, flexible leads, resistance and connecting wire, keys and switches, lamps and lamp holders, an electric bell and linkable cell holders. The specifications below are the ones given in each listing.

Keys and switches

Item	What the listing specifies
Plug Key One Way	Two brass blocks 9 mm thick with brass terminals on a Bakelite base; tapered plug with a moulded Bakelite top
Plug Key Three Way	Four brass blocks 9 mm thick on a Bakelite base, with the same tapered plug
Plug Key, Four Way	Commutator plug: four brass quadrants on a circular Bakelite block
Charge and Discharge Key	For charging and discharging a capacitor; three terminals on a thick Bakelite plate; contact resistance 2 milliohms; maximum 5 A
Single Knife Switch	Single pole, double throw, on a Bakelite base with screw holes for bench fixing
Double Knife Switch	Double pole, double throw, on a Bakelite base with screw holes
Reversing Switch	Rotary brush type with phosphor-bronze contacts; maximum 10 A; screw terminals
Pohl’s Commutator	For hysteresis experiments; brass contact arms on a Bakelite base with a Bakelite handle; maximum 5 A; supplied without mercury
Telegraph Key	Contact key on a solid plastic base, 11 x 5 cm
Electric Bell On/Off Push	Moulded plastic body with screw holes

Plugs, sockets, clips and leads

Banana Plug: 4 mm pin with an 18 mm spring insert and solder nipple, on a screw-on plastic body about 40 mm long.
Banana Plug Socket: 4 mm moulded socket with fixing nut for an 8 mm panel hole, panels up to 12 mm thick; plated brass insert with solder pin; red, black, yellow and blue.
Terminal Socket: screw top for wires and spade terminals, with a 4 mm socket, a 5 mm gap for crocodile clips and a 2 mm hole for bare leads.
Stackable Plugs: 4 mm, ABS body, with screw connections and extra 4 mm holes along and across for further plugs.
Spade Socket Connector: plated spade terminations in an insulated shank with 4 mm end sockets.
Crocodile Clips: spring-loaded serrated jaws, screw clamp for the lead, insulated thumb-press grip; black and red.
Connection Strip: moulded plastic strip with two rows of clamping screws, which can be cut into shorter blocks.
Flexible Leads, Banana Plugs (4 mm plugs both ends), Flexible Leads, Banana Plug and Crocodile Clip (1000 mm) and Flexible Leads Crocodile Clip (360 mm, pack of 10, shrouded clips).
Flexible Leads, 10 Wire Ribbon: a flat ribbon of ten coloured wires with 4 mm red plugs at one end and black at the other.

Wire, lamps, bell and cells

Item	What the listing specifies
Bare Manganin Wire	Manganese-nickel-copper alloy with a low temperature coefficient, for accurate resistance at low loading; 125 g reel
Bare Constantan Wire	Copper-nickel alloy with a low temperature coefficient, for resistance coils; 125 g reel
Bare Copper Wire	High-conductivity copper; 125 g reel
Copper Wire, Insulated	Flexible annealed copper with a thin plastic coating, for coils and transformers; rolls of 90 m
Flash Lamp (S.B.C)	Low-voltage clear bulb with axial filament and SBC base; 1000 hours rated life; 55 mm long, 38 mm wide
Lamp Holder	MES holder for flash lamp bulbs, plated brass shell in a plastic base, two screw connections
Lamp Holder Mounted	Holder on a rectangular moulded base with two 4 mm sockets; a second listing carries an SBC double-contact holder
Electric Bell	Detachable plastic cover to show the working; listed for the bell-in-a-bell-jar experiment and other electromagnetic work
Cell Holders	Single 1.5 V units that link electrically and mechanically to make battery boxes of any voltage

Compasses

The Plotting Compass has a needle pivoted between glass plates with no dial, in a 20 mm aluminium case, for tracing field lines. The Pocket Compass with Cover is 45 mm across, graduated in degrees, with a needle lock and hinged cover for transport.

Related ranges

These components serve the whole Electricity & Magnetism range. Kits and capacitance boxes are under Circuit, resistance boxes and bridges under Resistance, and magnetic needles and the dip circle under Magnetism.

Questions buyers ask

Which wire is used to make resistance coils?
Manganin and constantan. Both are listed with a low temperature coefficient; constantan is named for resistance coils, and manganin for work where an accurate ohmic value matters at low loading.

Which key is for capacitor charging experiments?
The Charge and Discharge Key, with three terminals, 2 milliohm contact resistance and a 5 A maximum.

Are the plugs and sockets one standard?
The plugs, sockets, stackable plugs and most leads in this range are listed as 4 mm, so they connect to one another and to 4 mm terminals on other apparatus.

How are cells combined into a battery?
The Cell Holders are single 1.5 V units designed to link together, so a battery box of the voltage needed is built from several.