Exam 25: Electric Current and Direct-Current Circuits

When two resistors are connected in series,the equivalent resistance is R_s = 10 $\Omega$ .When they are connected in parallel,the equivalent resistance is R_p = 2.4 $\Omega$ .What are the values of the two resistances?

When two identical resistors are connected in series across a battery,the total power dissipated by them is 20 W.If these resistors are connected in parallel across the same battery,the total power dissipated is

A 20.0- $\mu$ F capacitor is charged to 200 V and is then connected across a 1000- $\Omega$ resistor.What is the initial current just after the capacitor is connected to the resistor?

An uncharged capacitor and a resistor are connected in series to a battery as shown. If $\varepsilon$ = 15 V,C = 20 $\mu$ F,and R = 4.0 $\times$ 10⁵ $\Omega$ ,the charge on the capacitor as a function of time is

The current in a wire varies with time according to the relation where I is in amperes and t is in seconds.The number of coulombs of charge that pass a cross section of the wire between t = 3 s and t = 5 s is

The resistivity of any given metal

In a certain particle accelerator,a current of 800 $\mu$ A is carried by a 6.00-MeV proton beam that has a radius of 1.50 mm.The mass of a proton is 1.67 $\times$ 10^-27 kg.How many protons per unit volume are in this beam?