Abattery applies 45 volts to a circuit, while an ammeter reads 10 ma. later, the ammeter reading drops to 7 ma. assuming the resistance has not changed, the voltage must have

This can be computed using Ohm's law relates the voltage, current and resistance using the following relation:

V = I * R

Where:

V is the applied voltage

I is the current

R is the resistance

We can say that the voltage and current are straight related to each other supposing there is continuous resistance. Meaning that when the current decreases, the voltage must have decreased as well.

So let us calculate the new voltage:

Voltage = 45 volts

Current = 10 ma = 10*10^-3 ampere

Substituting in the above relation:

V = IR

R = V/I = 45/10*10^-3 4500 Ω

Well along, the current released to 7*10^-3 ampere and the resistance is reserved the same.

So using the old equation: V = IR = 7*10^-3 * 4500 = 31.5 volts

Therefore, the voltage decreases as the current decreases.

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:

unlike poles attract