The figure shows an electrical circuit

D.C.

Option number 1.

1. 
   How many times did the resistance of the conductor decrease if the amount of heat released during the flow of current through it increased by 3 times? The voltage applied to the conductor and the current flow time do not change. Justify the answer.

1. 
   A galvanic cell with an EMF of 1.5 V and an internal resistance of 1 ohm is closed to an external resistance of 4 ohms. Find the voltage drop across the external resistance. Express the result in SI units.

1. 
   The electric kettle has two windings. When you turn on one of them, the water boils after 15 minutes, when you turn on the other - after 30 minutes. How long will it take for the water to boil in the kettle if both windings are connected in parallel? Present the result in minutes.

1. 
   The motor of an electric train when moving at a speed of 54 km/h consumes a power of 900 kW. The efficiency of motors and transmission mechanisms is 0.8. Find the thrust force of the motors. Express the result in kilonewtons and round up to a whole number.

D.C.

Option number 2.

1. 
   A conductor with a resistance of 30 ohms was connected to the poles of a current source with an EMF of 8 V. In this case, the voltage between the ends of the conductor is 6 V. What is the internal resistance of the current source? Express the result in SI units.

1. 
   When the element is shorted to a resistance of 2.3 Ohm, the current in the circuit is 0.56 A, and when the element is shorted to a resistance of 1.8 Ohm, the current in the circuit
   0.7 A. Determine the short circuit current.

1. 
   Nickel plating of a metal product with an area of ​​120 cm 2 lasted 5 hours at a current of 0.9 A. Determine the thickness of the nickel layer on the product. Faraday number 96500 C/mol, nickel density 810 3 kg/m 3 , nickel valency 1, nickel atomic mass 0.058 kg/mol. Give your answer in micrometers (1 µm = 10 -6 m) and round to the nearest whole number.

D.C.

Option number 3.

1. 
   Find the short-circuit current of the battery if, at a current of 5 A, the battery outputs 9.5 W to the external circuit, and at a current of 8 A, respectively, 14.4 W. Express the result in SI units and round to the nearest whole number.

1. 
   A rheostat is connected to a source with an EMF of 12 V and an internal resistance of 1 ohm, the resistance of which is 5 ohms. Find the voltage at the source terminals. Express the result in SI units.

1. 
   An electric lamp with a resistance of 240 ohms, designed for a voltage of 120 V, must be powered from a network with a voltage of 220 V. How long should a nichrome conductor with a cross section of 0.55 mm 2 be connected in series with the lamp? The specific resistance of nichrome is 11010 -8 Ohmm. Express the result in SI units.

1. 
   During the electrolysis of a sulfuric acid solution, 0.3 g of hydrogen was released in 50 minutes. Determine the power spent on heating the electrolyte if its resistance is 0.4 ohm. Faraday number
   96500 C/mol, molar mass of hydrogen 2 g/mol, valence 1. Express the result in SI units and round to the nearest whole number.

D.C.

Option number 4.

1. 
   How many times is the total resistance of two conductors having resistances R and 0.5 R, connected in series, more or less than the total resistance of the same conductors connected in parallel?

1. 
   With a current strength of 3 A, a power of 18 W is released in the external circuit, and with a current strength of 1 A, respectively, 10 W. Determine the EMF of the source. Express the result in SI units.

1. 
   An element with an EMF of 2 V has an internal resistance of 0.5 ohms. A current of 0.25 A flows in a circuit with an external resistance R. What is the external resistance R of the circuit under these conditions? Express the result in SI units.

1. 
   Into how many equal parts should the conductor be cut so that, when these parts are connected in parallel, the resistance is 25 times less than the resistance of the entire conductor?

1. 
   A balloon with a volume of 250 m 3 is filled with hydrogen at a temperature of 27 ° C and a pressure of 210 5 Pa. How much electricity must be passed through a weak solution of sulfuric acid to obtain the required amount of hydrogen? The electrochemical equivalent of hydrogen is 1.04410 -8 kg/C, the universal gas constant is 8.31 J/(Kmol). The molar mass of hydrogen is 2 g/mol. Present the result in GKL
   (1 GC = 10 9 C) and round to the nearest whole number.

D.C.

Option number 5.

1. 
   Two lamps 1 and 2 are connected in parallel to the network. The resistance of lamp 1 is greater than the resistance of lamp 2. Which of the lamps (1 or 2) will release more heat in an equal time? Justify the answer.

1. 
   When repairing an electric stove, its spiral was reduced by 0.1 of its original length. By how many times did the power of the electric stove increase? Round the result to tenths.

1. 
   Two light bulbs with resistances of 360 ohms and 240 ohms are connected to the network for the first time in series, the second time in parallel. How many times the power absorbed by the bulbs when connected in parallel is greater than when connected in series? Round the result to the nearest hundredth.

1. 
   The galvanic cell closes once to a resistance of 4 ohms, another time to a resistance of 9 ohms. In both cases, the amount of heat released in the same time is the same. What is the internal resistance of the element? Express the result in SI units.

D.C.

Option number 6.

1. 
   In a network with a voltage of 220 V, two light bulbs for a voltage of 110 V each are connected in series. During operation, one bulb burned out. What current will flow through the remaining bulb? Justify the answer.
2. 
   The winding of the rheostat with a resistance of 84 ohms is made of nickel wire with a cross-sectional area of ​​1 mm 2 . What is the length of the rheostat wire? The specific resistance of nickeline is 0.42 Ohmmm 2 /m. Express the result in SI units.

1. 
   The strength of the anode current in the radio tube is 12 mA. How many electrons reach the lamp's anode in 1 second? Electron charge 1.610 -19 C.

1. 
   Determine the resistance of the shunt of the school galvanometer, which needs to measure current up to 10 A, if the resistance of the galvanometer without a shunt is 0.25 Ohm, and its scale is designed for 5 mA. Express the result in SI units and round to the nearest hundredth.

1. 
   EMF source 2 V, internal resistance 1 ohm. At what values ​​of current strength does the external circuit consume 0.75 W of power? Express the result in SI units.

D.C.

Option number 7.

1. 
   Determine the cross section of the nichrome wire of the rheostat with a resistance of 5 ohms, if the length of the rheostat wire is 20 m. Present the result in mm 2 and round to tenths.

1. 
   A battery with an EMF of 1.45 V in a 2.5 ohm conductor creates a current of 0.5 A. Determine the current in the event of a short circuit in the battery. Express the result in SI units.

1. 
   A welding machine with a resistance of 0.1 ohms operates at a current of 200 A for 7 hours. Determine the cost of electricity spent in this case, if the cost of 1 kWh of energy is 40 kopecks. Present the result in rubles.

D.C.

Option number 8.

1. 
   How many times will the amount of heat released during the flow of current through the conductor decrease if the resistance of the conductor is increased by 5 times? The voltage applied to the conductor and the current flow time do not change. Justify the answer.

1. 
   There is a voltmeter designed to measure the potential difference up to 30 V, the resistance of which is 2 kOhm. What additional resistance should be taken in order to measure voltage up to 75 V with this voltmeter? Express the result in SI units.

1. 
   The heating element of the electric soldering iron is made of nichrome wire with a resistance of 200 ohms at 0 ° C. When the soldering iron is heated, the resistance of the wire increases to 236 ohms. Determine to what temperature the nichrome wire is heated. The temperature coefficient of nichrome is 210 -4 deg -1. Give your answer in degrees Celsius.

1. 
   What amount of heat will be released in the conductor, through which a current of 3 A flows for 3 minutes, if a voltage of 0.5 V is applied to the ends? Express the result in SI units.

1. 
   A shunt is connected to a galvanometer with a resistance of 290 ohms, which reduces the sensitivity by 10 times. What resistance must be connected in series with a shunted galvanometer so that its total resistance remains the same? Express the result in SI units and round to the nearest whole number.

D.C.

Option number 9.

1. 
   How did the resistance of the conductor change if the amount of heat released during the flow of current through it increased by 2 times? The voltage applied to the conductor and the current flow time do not change. Justify the answer.

1. 
   A current source with an EMF of 100 V and an internal resistance of 1 ohm is included in a circuit with a resistance of 19 ohms. Determine the current in the circuit. Express the result in SI units.

1. 
   The resistance of the electromagnet winding, made of copper wire, at 0 ° C was 2 ohms, and after prolonged operation it became 2.4 ohms. What is the temperature of the winding? The temperature coefficient of resistance of copper is 0.0043 1/K. Express the result in degrees Celsius and round to the nearest whole number.

1. 
   During 40 s, a certain amount of heat was released in a circuit consisting of three identical conductors connected in parallel and included in the network. How long will the same amount of heat be released if the conductors are connected in series? Express the result in SI units.

1. 
   An incandescent light bulb consumes a current of 0.2 A. The diameter of a tungsten hair is 0.02 mm. The temperature of the tungsten when the lamp is burning is 2000 ° C. Determine the field strength in the hair, considering the field to be uniform. Resistivity of tungsten
   5.310  8 Ohmm at 0 o C, temperature coefficient of resistance 1/273 1/K. Express your answer in SI units and round to the nearest whole number.

D.C.

Option number 10.

1. 
   A current source with an internal resistance of 1 ohm is connected to a circuit with a resistance of 9 ohms. A current of 10 A flows through the circuit. Determine the EMF of the current source. Express the result in SI units.

1. 
   Two conductors of the same size, one copper, the other nichrome, are connected in parallel to the current source. How many times greater is the current in a copper conductor than in a nichrome conductor? Resistivity of copper is 1.710 -8 Ohmm, nichrome - 1.110 -6 Ohmm. Round your answer to the nearest whole number.

1. 
   The power line has a resistance of 250 ohms. What voltage should the generator have so that when transmitting 25 kW through this line to a power consumer, energy losses do not exceed 4% of the power transmitted to the consumer? Express the result in kV and round up to a whole number.

1. 
   Determine the resistance of the supply wires from a 120 V source with a negligible internal resistance, if, during a short circuit, a lead wire fuse with a cross-sectional area of ​​\u200b\u200b1 mm 2 and a length of 2 cm melts in 0.03 s. The initial temperature of the fuse is 27 ° C. Take for lead: resistivity 2110 - 8 Ohmm; density 11400 kg/m 3 ; specific heat capacity 0.13 kJ/(kgK); melting point 327 about C; specific heat of fusion 25 kJ/kg. Give your answer in SI units and round to the nearest hundredth.

ANSWERS

On the topic “DIRECT CURRENT. school"