Physics Current Electricity Level: High School
A tungsten wire is used to determine the melting point of indium . The resistance of the tungsten wire is 3.000 ohm at 20 dgreeC and increases to 4.850 ohm as the indium starts to melt tungsten = 4.50 x 10- 3 (degreeC) -1. What s the melting temperature of indium ?a. 132 degreeC
b. 157 degreeC
c. 351 degreeC
d. 731 degreeC
Physics Current Electricity Level: High School
A metal wire has a resistance of 25.00 ohm . Under room temperature conditions of 25 degreeC when the wire is heated to 85 degreeC the resistance increases by 0.75 ohm . What is the temperature coefficient of resistivity of this metal ?a. 5.0 x 10-4(degreeC)-1
b. 1.3 x 10-3(degreeC)-1
c. 1.5 x 10-3(degreeC)-1
d. 2.5 x 10-3(degreeC)-1
Physics Current Electricity Level: High School
Number 10 copper wire (radius = 1.3mm) is commoly used for electrical installation in homes .What is the voltage drop in 40 m of #10 copper wire if it carries a current of 10A? (The resistivity of copper is 1.7 x 10-8 ohm.m .)a. 1.3 V
b. 0.77 V
c. 0.50 V
d. 0.13 V
Physics Current Electricity Level: High School
A flashlight bulb operating at a voltage of 4.5 V has a resistance of 8.0 ohm . How many electrons pass through the bulb filament per second (e = 1.6 x 10-19 C) ?a. 3.7 x 1016
b. 1.8x 1021
c. 9.4 x 1017
d. 3.5 x 1018
Physics Current Electricity Level: High School
A high voltage transmission line of diameter 2 cm and length 200 km carries a steady current of 1000A . If the conductor is copper with a free charge density of 8 x 1028 electrons/m3 , how long does it take one electron to travel the full length of the cable ? (e = 1.6 x 10-19 C)a. 8 x 102 s
b. 8 x 104 s
c. 8 x 106 s
d. 8 x 108 s
Physics Current Electricity Level: High School
When an electric current exist s within a conducting wire , which of the following statement describes the condition of any accompanying electric field ?a. must be zero .
b. must be parallel to current flow .
c. Must be anti-parallel (opposite direction) to current flow .
d. must be perpendicular to current flow .
must be parallel to current flow .
Physics Current Electricity Level: High School
If a metallic wire of cross sectional area 3.0 x 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 x 1028 carriers/m3 , What is the average drift velocity of the mobile charge carriers ? (charge value = 1.6 x 10-19 C)a. 3.4 x 103 m/s
b. 1.7 x 103 m/s
c. 1.5 x 10-4 m/s
d. 2.9 x 10-4 m/s
Physics Current Electricity Level: High School
The current in an electron beam ina cathode –ray tube is measured to be 70 A . How many electrons hit the screen in 5.0 s ? (e=1.6 x 10-19 c)a 2.2 x 1011 electrons
b . 8.8 x 1013 electrons
c. 2.2 x 1015 electrons
d. 8.8 x 1018 electrons
Physics Current Electricity Level: High School
Initially the capacitor is uncharged , and the switch is open . At t = 0, the switch is closed . The positive direction of the currents are represented by arrows in the diagram which is shown at “click here”a) Calculate the charge on the positive plate of the capacitor jus tafter the switch is closed.
b) Calculate the following currents immediately after the switch is closed.
. I1(0+) = A
. I2(0+) = A
c) After the switch has been closed for a long time , calculate the following quantities :
. I1= A
. I2= A
. Q= C
d) At some yet later time T, the switch is again opened . Calculate the following currents immediately afterward .
I1(T+) = A
I3(T+) = A
e) What is the time constant of the discharging circuit ?
Physics Alternating Current Level: High School
In the figure at “click here” each of the resistors in the circuit to the left has a resistance of 4.3 ohm.a). What is the equivalent resistance between points F and H ?
b. ) What is the equivalent resistance between points F and G ?
Physics Current Electricity Level: High School
When the lights on an automobile are switched on , an ammeter in series with them read 9A and a voltmeter connected across them read 12 V . When the electric starting motor is turned on, the ammeter reading drops to 6A and the light dims somewhat . You may assume that the ammeter and the voltmeter are ideal , The internal resistance of the battery is 0.04ohm .a). What is the EMF of the battery ?
b). What is the current running through the starting motor when the lights are on?
c). Now positions of the voltmeter and the ammeter is interchanged in the circuit as shown in the figure at “click here “ . The switches are set so that the lights can turn on but the starting motor will not. what is the current flowing through the lights ?
Physics Current Electricity Level: High School
A 3.5 M ohm and a 2.2 micro F capacitor are connected in series with an ideal battery with an EMF of 4 V. At 3 seconds after the circuit is initially connected to the battery :a. What is the rate at which the charge on the capacitor increasing ?
b. What is the rate at which energy is being stored on the capacitor ?
c. What is the rate at which thermal energy is appearing in the capacitor ?
d. What is the rate at which energy is being delivered by the battery ?
Physics Current Electricity Level: High School
In the circuit as shown in the figure at “click here” has. E = 2V
. r=80 ohm
. R1 = 280 ohm
. R2 = 360ohm
. Internal resistance of the voltmeter = 6 x 10^3 ohm
. The ammeter is ideal (ie, its internal resistance is zero )
(a) What is the magnitude of the percentage error the voltmeter introduces when trying measure the potential difference across R1 ?
Physics Current Electricity Level: High School
The circuit in the figure which is shown at ‘click here” is composed of two batteries ( E1=5V and E2=4V ) and three resistors (R1 = 3ohm, R2 = 3ohm, R3=4ohm) as shown.a . What is the current I 3 flowing through the batteries ?
b . What is the voltage Vb-Va between the points a and b in the circuit ?
Physics Current Electricity Level: High School
The point b and c on the diagram at “click here” are the terminals of a battery with EMF E and internal resistance r. the circuit resistors have the following values : R1 = 37 ohm, R2 = 41 ohm, R3 = 51 ohm, R4 = 56 ohma. An ideal voltmeter is connected between b and c; it reads Vc-Vb = 12V. What is the EMF of the battery ?
b. What resistance would an ohmmeter connected across points a and c read ?
c. An ideal ammeter is inserted between points a and b it reads 0.19A. Determine the internal resistance of the battery ?
d. What does the voltmeter connected across b and c read now ?
e. Calculate the magnitude of the current through R2 .
f. At what rate is thermal energy (heat) being produced inside the battery ?
g. What is the power being provided by the battery to the external circuit (outside the battery)
