metal cap is the negative terminal of an electric cell true or false please send me the answer please

Ais useful when you need a simple machine to you separate two things. a. lever b. screw c. pulley d. wedge

If y gets smaller as x gets bigger and y have an relationship?

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.