Non inductive resistor

I presume non-inductive would mean anything other than wire-wound, but stand to be corrected.

Some (all ?) of the standard modern film resistors are made by depositing conductive film on a cylindrical former and then cutting a spiral groove in it to leave a spiral conductive path of just the right resistance. Obviously a spiral thing will have inductance - not much inductance, but some. The old carbon composition resistors were a lump of solid which would have had less inductance. And it is possible to get 'non-inductive' wirewounds (they consist of counter-wound layers whose magnetic fields cancel) but these are unusual. If in doubt you can check the manufacturer's datasheet.

VB

Thanks, that answered my question. Knew this would be the right place to confirm my though.

An interesting and unusual design is the so-called Möbius resistor. This consists of two resistive strips (e.g., Manganin) that are separated by a thin insulating material. A single twist is introduced and the ends are connected together, thus forming a Möbius strip.

This arrangement means that, at any point on the loop, the currents are flowing in opposite directions and hence the magnetic fields cancel. With no magnetic field there can be no inductance. This design works particularly well for high currents at high frequencies - the resistor has a flat frequency response up to several hundred MHz. It also means that the resistor does not generate magnetic fields that could influence other parts of the circuit; similarly it will ignore externally generated fields. It does not interact with itself or with its surroundings.

This was not an April spoof; the Möbius resistor was patented back in the sixties and is still used in EMC test laboratories where they have to measure current at frequencies up to 800 MHz or thereabouts.

Having said that, I do like your Australian colour TV spoof. Many years ago a friend and I secretly fitted an unobtrusive switch to the back of his Dad's TV that would reverse the frame scan coils. We had a hilarious evening on April 1st watching the TV to see how long it took his Dad to notice!

60 years ago there was a third trade magazine that circulated alongside the better known pair on a monthly basis, published by RTRA. It was called Radio Retailer and featured a column called Counter Talk written by an independent retailer.

One month he reported that he'd gone into town one evening and paused opposite his shop for a while. Despite its attractive and well illuminated display he noted that, almost without exception, pedestrians just walked past taking absolutely no notice at all.

The following day he reversed the field scan coils of a set that sat prominently in the centre of his display. Making another return visit later in the evening he was delighted with the results. Pedestrians would walk by as before until, at the last moment, they would stop dead in their tracks, turn, and walk towards his window where a card prominently stating "SPECIAL DESIGN FOR AUSTRALIA" sat on top of the set. Whilst some would just laugh and walk on, he noted that a large number would wait a little longer, glancing over the rest of his display in the process.

In the 60s, a component shop not far from where I now live - Ben Salmon Radio in Romford Road, Manor Park E12, was famous for the outrageous claims made for various humble components in its window display. It was always worth having a good look at the display whenever possible which was always good for a little chuckle or two ...

Unfortunately, such practices came to an abrupt stop with the passing of the Trades Description Act, 1968.

It was a long time before someone discovered that the Act could be circumvented easily by simply adding the word 'possibly' to the description ...