Question

1.

Answer 1

The voltage needed = 120 V

Further explanation

Electric current (symbolized by the letter "i) is the amount of charge flowing in the conductor of each unit of time  

Can be formulated:  

$\large{\boxed{\bold{I=\frac{Q}{t}}}$

Q = charge (Coulomb)  

t = time (seconds)  

The international standard unit of electric current is Coulomb/second or Ampere (A).  

Electric current is also a ratio between the voltage and the amount of resistance at the conductor.  

Can be formulated  

$\large{\boxed{\bold{I=\frac{V}{R}}}$

V = Voltage (volts)  

R = resistance (ohms)  

I=current=4 A

R=resistance=30 Ω

The voltage needed :

$\tt V=I\times R\\\\V=4\times 30\\\\V=\boxed{\bold{120~V}}}$