3289

Physics Current Electricity Level: High School

Heating effect of current

One light bulb is marked “15 W 120 V” and another “60 W 120 V” . This means that each transforms this amount of electrical energy into light and heat per second when plugged into a constant 120-V potential difference . (You may assume 3 significant digits for the markings) .

a) Find the resistance of each bulb . When they are connected to a 120 V power supply which bulb is brighter ?

b) How longs does it take for 1.00 C to pass through the dim bulb ? How is this charge different upon its exit versus its entry into the bulb ?

c) How long does it take the dim bulb to dissipate 1.00 J of energy ?

d) Find the cost of running the dim bulb continuously for 30.0 days if the electric company sells its product at $0.800 per kilowatt-hour (kWh) .

e) What physics quantity does the electric company sell ? What is the price for one SI unit of this quantity ?

f) Assume you can buy gasoline at $2.00 gallon and each gallon contains 114000 Btu . What is the ratio of the cost energy from the electrical power company over the cost of energy from the gas pump ?

3227

Physics Current Electricity Level: High School

Ohm's law

A steam iron draws 4.0 A when connected to a potential difference of 116V.

a) What is the poer rating of this iron? In units of W.

b) How much energy is produced in 20 min? In units of J.

c) How much does it cost to run the iron for 20 min at $ 0.010/kW-h? Answer in dollars.

2895

Physics Current Electricity Level: High School

EMF of a Battery

Complete the following statement . The electromotive force is

a) the maximum potential difference between the terminals of a battery

b) the force that accelerates electrons through a wire when a battery is connected to it .

c) the force that accelerates protons through a wire when a battery is connected to it .

d) the maximum capacitance between the terminals of a battery .

e) the maximum electric potential energy stored within a battery .

2613

Physics Current Electricity Level: High School

Combination of resistors

Find the equivalent resistance for all of the resistors in the figure at “click here” . The resistance is given in ohms .

2580

Physics Current Electricity Level: High School

Resistance

A 6.0 volt battery is connected in parallel with two identical lamps , each having a resistance of 24 ohms , Under these conditions , the resistance of the battery is negligible .

a) Calculate the total resistance of the lamps ?

b) Calculate the current flowing through each lamp ?

c) Calculate the power consumption of each lamp .

d) What would happen to the current drawn from the battery if one of the lamps burnt out ?

e) Would it be hazardous if you stuck your finger in one of the lamp socket with the battery connected ? Why ?

2070

Physics Current Electricity Level: High School

A 29 V battery has an internal resistance r . What is the value of r ? Answer in units of Ohm .

Determine the magnitude of the current through the 90 Ohm resistor on the right-hand side of the circuit . Answer in units of A .

2069

Physics Current Electricity Level: High School

A 20 V battery delivers 107 mA of current when connected to a 73 Ohm resistor . Determine the internal resistance of the battery . Answer in units of Ohm .

2066

Physics Current Electricity Level: High School

When switch S is open , the ammeter in the circuit shown reads 2.0 A . when S is closed , the ammeter reading :

a) Increases slightly .

b) Remains the same .

c) Decreases slightly .

d) Double .

e) Halves .

2062

Physics Current Electricity Level: High School

A battery with an emf of 24 V is connected to a 6-Ohm resistor . As a result , current of 3 A exists in the resistor . The terminal potential difference of the battery is :

a) 0

b) 6 V

c) 12 V

d) 18 V

e) 24 V

2059

Physics Current Electricity Level: High School

By using only two resistors, R1 and R2 , a student is able to obtain resistance of 3 Ohm , 4 Ohm , 12 Ohm , and 16 ohm using them alone or in combination . The value of R1 and R2 (in Ohms) are ?

a) 3,4

b) 2,12

c) 3,16

d) 4,12

e) 4,16