A transformer with 1000 turns in its primary coil has to reduce the voltage from 4400 V to 220 V for home use. How many turns must there be on the secondary coil?

A student in the laboratory connects a $10-\Omega$ resistor, a $15-\Omega$ resistor, and a $20-\Omega$ resistor in series and then connects the arrangement to a $50-\mathrm{V} \mathrm{dc}$ source. (a) How much current is in the circuit? (b) How much power is expended in the circuit?

A $30.0-\Omega$ resistor and a $60.0-\Omega$ resistor in series are connected to a $120-\mathrm{V}$ dc source. (a) What is (are) the current(s) through the resistors? (b) What is the voltage drop across each resistor?

Assume the two resistors with values of $25 \Omega$ and $35 \Omega$, respectively, were connected in parallel. What would be the current and the power in this case?

A $24-\Omega$ component is connected to a $12-\mathrm{V}$ battery. Find out how much energy is expended per second.

How much does it cost to run a 1500 -W hair dryer 30 minutes each day for a month ( 30 days) at a cost of $12 \%$ per kWh?

A car radio draws 0.25 A of current in the auto’s 12-V electrical system. Find out how much electric power does the radio use. What is the effective resistance of the radio?

The heating element of an iron operates at 110 V with a current of 10 A. Identify the resistance of the iron. What is the power dissipated by the iron?

How much current flows through an electrical component with a resistance of $50 \Omega$ when connected to a 120-V source?

What are the forces on two charges of $+0.60 \mathrm{C}$ and $+2.0 \mathrm{C}$, respectively, if they are separated by a distance of $3.0 \mathrm{~m}$ ?

To separate a 0.25-C charge from another charge, 30 J of work is done. What is the electric potential energy of the charge?

There is a net passage of $4.8 \times 10^{18}$ electrons by a point in a wire conductor in $0.25 \mathrm{~s}$. Identify the current in the wire.

How many electrons compose one coulomb of charge? (Clue: q = ne.)

To separate a 0.25-C charge from another charge, 40 J of work is done. What is the voltage of the 0.25-C charge?