Electricity And Magnitism, Resistance

This problem is easy.Ohms Law is $V=IR$ so now you substitute $12v=2.5*10^3*(R)$ By simple divison the answer is $4.8*10^3$ as we are told the the answer is $\boxed{4.8kW}$ .

$Resistance\quad (R)\quad of\quad a\quad resistor\quad is\quad given\quad by\quad Ohm’s\quad law\quad as,\\ \\ \quad V=IR\\ \\ \quad R=\frac { V }{ I } \\ \\ Where\quad Potential\quad difference\quad V\quad =12V\\ \\ Current\quad in\quad the\quad circuit\quad =\quad 2.5\times { 10 }^{ -3 }\\ \\ R=\frac { 12 }{ 2.5\times { 10 }^{ -3 } } \\ \\ R=\quad 4.8\times { 10 }^{ 3 }\Omega \\ \\ R=\quad 4.8kW$

v=IR . so 12/2.5=4.8