Very easy physics maths about current and other stuffs only one question please help me

Three identical resistors of resistance 3 ohms are connected in series in a circuit. What is the total voltage of the battery if the current in the circuit is 2A ?

Total voltage of the battery is 12 volts.

Explanation:

It is given that, we have three identical resistors of resistance 3 ohms are connected in series in a circuit. It is required to find the total voltage of the battery if the current in the circuit is 2 A.

Let is the equivalent resistance in series combination. The equivalent resistance is given by :

Let V is the total voltage of the battery. Ohm's law is given by :

So, the total voltage of the battery is 12 volts.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.