I want to make a simple circuit. I want to connect a bulb, buzzer and switch to a battery. About the size we all used in science at school. When the switch is on, I want the buzzer and bulb to work together. Do I need to use resistors and transistors? I have no idea. Help!
If you are using a readymade buzzer, there is no need to buy transistors etc (an internal oscillator, containing a coil, a transistor and few resistors already given in that buzzer), and the circuit you're trying to make, is very simple.
The only-thing you have to keep in notice, that, electric current goes through the wire just like water flows through pipe. The batteries work like pump. one end of the battery (+ve end) pumps-out the positive charges, and the other-end of the battery, sucks-in the positive-charge. Keeping-it in mind , you can alter the placement of parts, make a "circuit" or a complete circular path , and test the circuit is working or not.
If you're using a readymade buzzer,
keep in mind, it contains 2 wires, of different nature (polarity). Red wire is positive input to buzzer, black-one is negative-input to buzzer.
LED vs Bulb ?
LED is a kind of semiconductor-diode that gives light when in forward bias. it is not bulb in true-sense. however, LEDs are now being used widely, since they're durable and cheap. But LEDs have polarity.
Anode is the positive input pole, and cathode is the negative input pole.
You could also use small bulbs (torch bulbs), but they are nowadays rare in market.
Bulbs need no specific polarity
but usually, torch-bulbs have one end at bottom, and other end at side, shown in the image. http://www.ekshiksha.org.in/images%20of%20Electricity_and_Circuits_VI/3.png
You could take 1.5Volt or 3Volt batteries in different numbers, all in series combination, to adjust voltage. usually an LED cuts-open before 7.5V or 12V, however in a series or parallel combination , the LED gets lesser voltage from the same source, so needs quite higher voltage. A readymade piezo-buzzer is usually loud enough,. so I guess three or four 1.5V batteries maybe enough.