For example, say I hook up a 12 volt ac-dc converter for a portable dvd player to a 12 volt car battery? Would it work fine, or would I need to do something special to make it work?

A: At best it will not work, at worst it will damage the converter.

The Car battery is already 12 V DC, so provided it provides enough current, you should be able to connect the DVD player directly to the car battery.

See if they sell a car-battery power cable that fits your player.

40. A transformer has an input of 9 volts and an output of 36 volts. If the input is changed to 12 volts, what will the output be? -
41. A portable CD player requires 12 volts to operate correctly. A transformer nicely allows the device to be powered from a 120-volt out-let. If the primary has 500 turns, how many turns should the secondary have? -
42. A model electric train requires a low voltage to operate. If the primary coil of its transformer has 400 turns, and the...

40. A transformer has an input of 9 volts and an output of 36 volts. If the input is changed to 12 volts, what will the output be? -
41. A portable CD player requires 12 volts to operate correctly. A transformer nicely allows the device to be powered from a 120-volt out-let. If the primary has 500 turns, how many turns should the secondary have? -
42. A model electric train requires a low voltage to operate. If the primary coil of its transformer has 400 turns, and the...

If you haven't been shopping for camping gear in a while, let me just tell you things have changed. It could be argued that some of this is for the best, but in some cases, products on the shelves seem a little outrageous. Pre-packaged, sharpened marshmallow sticks are sold -- case in point.

I'll admit I've never tried store-bought marshmallow roasting sticks, so perhaps I should reserve judgment. Just the same, are we at a point in society where we need to buy sticks whose sole purpose is to hold a sticky, sugary confection above a fire for a few seconds?

Perhaps pre-made marshmallow sticks save campsites to a degree by reducing the wood scavenging that leaves so many campsites looking unnaturally open and bare, but still, I have a hard time with this one. Can't campers bring a bug free stick (watch out for invasive beetles, etc.) that they took two minutes to craft into a marshmallow skewer?