Ohm s Law Practice Questions Answers Physics Electricity Good Speed Enters!

1. Multiple choice questions (choose a correct answer, a total of 15 questions, 2 points for each question, 30 points).

1 According to Ohm's law, r=u i can be obtained, from which the following judgment is correct ( d ).

a.The resistance of a conductor is proportional to the voltage applied to it, and when the voltage is zero, the resistance is equal to zero.

b.The resistance of a conductor is inversely proportional to the current passing through it, and there is no resistance when no current passes through it.

c.The resistance of a conductor is equal to the ratio of the voltage applied to it to the current passing through it.

d.None of the above is true.

2 A student drew an image as shown in Figure 1 according to the collected data in ** "The relationship between current and voltage and resistance", and the following conclusion is consistent with the image (c).

a.When the resistance is constant, the current increases with the increase of voltage bWhen the resistance is constant, the voltage increases as the current increases.

c.When the voltage is constant, the current decreases with the increase of resistanceWhen the voltage is constant, the resistance decreases as the current increases.

3 As shown in Figure 2, AB and BC are two conductors of the same length and different cross-sectional areas made of the same material, which are connected into the circuit in series in series, and the voltage at both ends of these two conductors and the magnitude of the current passing through them are compared, and there is (C).

a. uab>ubc, iabubc, iab=ibc d.UAB = UBC, IAB U2 (fill in ".

The resistance of the first question d can be found by u i, but it has nothing to do with the voltage and current added to it, and the second question c resistor will change due to the increase of voltage and temperature, resulting in the decrease of current, so the explanation of ab error d is the same as above.

There's no picture in the back question.

From the diagram we know that the gap between the two plates is equivalent to the open circuit, and the resistance R2 is equivalent to the wire, then the lower plate and B are equipotential points, and the upper plate and A are equipotential points, then the voltage between the two plates is the same as the voltage of the sliding rheostat, i=e (R+R1+R 2), U plate = I*(r 2), from the balance of force: the charged droplet is balanced by gravity and electric field force, gravity is downward, the electric field force is upward, and the upper plate is positively charged, the lower plate is negatively charged, and the electric field line is downward, so the droplet is negatively charged, then mg=qe, e=u d, and U can be obtained by substituting the data, Lianli solution r

When a is reached, the current decreases, the voltage between the plates decreases, the electric field force decreases, the gravitational force is greater than the electric field force, the droplet moves downward, and the acceleration is solved by a=(mg-qe) m, and v is solved by the kinematic formula v 2=2*a*s

eq=mg, calculate e=2250V m, direction downward, and then by U=ed, calculate the voltage at both ends of the capacitor U=, the voltage at both ends of the capacitor is equivalent to the voltage at both ends of AB, and the sliding rheostat is connected in series with R1 and R, so the maximum value of East China rheostat is 45 ohms.

The second question, I am not too sure, it should be a downward acceleration movement, the reason, because it quickly to A, so quite a large resistance (voltmeter) at both ends of AB, so the combined resistance of Rab will become smaller, so the voltage at both ends of the sliding rheostat will become smaller, resulting in the destruction of the balance of the original electric field force and gravity, because you become smaller, so it will accelerate downward, as for the speed, use the conservation of energy to list an equation :)

To be honest, I don't even have a reward...

ps: The above answer is in the case that your diagram is not wrong...

Minimum resistance for fixed value resistance safety:

The voltage on the sliding rheostat: 6-4, the current is the same as the fixed resistance

The safe current of the voltmeter: the voltage on the sliding rheostat: 6-3, the current on the constant resistor:

The resistance is: 3 (3 16) = 16 ohms.

Then, the range is: 8-16

I'll give you some tips, but you have to be self-reliant, and you can't always rely on others.

Problems like this are generally column inequality groups, make sure that the sliding rheostat does not exceed the maximum current and voltage, and the voltmeter and ammeter do not exceed the maximum range, and then solve the inequality group.

However, there are fewer exams in this high school entrance examination, so don't worry too much.

The answer is A, first analyze the scribing to move to the left, the resistance of the sliding rheostat becomes smaller, the resistance of the fixed value resistance R remains unchanged, so the total resistance becomes smaller, according to Ohm's law, so the total current becomes larger, the voltage of the sliding rheostat becomes smaller, and because the series circuit R = R1 + R2, so the voltage of the fixed value resistance R becomes larger, the indicator of meter A becomes larger, and the indicator of meter V becomes larger, so C and D are excluded. The dicing moves to the right, the resistance of the sliding rheostat becomes larger, and the resistance value of the fixed value resistance R remains unchanged, so the total resistance becomes larger According to Ohm's law, the total current becomes smaller, and the voltage of the sliding rheostat becomes larger, and because of the series circuit R=R1+R2, the voltage of the fixed value resistance R becomes smaller, the indicator of meter A becomes smaller, and the indicator of meter V becomes smaller, so B is also wrong, only A is correct. Thanks for adopting!

Moving to the right, the slip access part becomes more and the resistance becomes larger, so the current representation number becomes smaller, and the voltage of the other resistor component becomes more, so the voltage representation number increases. Moving to the left, the slip input part becomes less, and the resistance becomes smaller, so the current representation number becomes larger, and the voltage of the other resistor becomes less, so the voltage representation number becomes smaller.

R is connected in series with P, A is to measure the trunk current, and V is the voltage on R;

p moves to the right, p increases, current i decreases, the indication of a decreases, and the indication of v also decreases;

P moves to the left, P decreases, current i increases, the indicator of A increases, and the indicator of V also increases.

Ohmic formula r=p·l s, so take a few points to solve p and r by simultaneous equations, the power dissipation current should be i=e (r+r), the power consumption is i2·r, find the maximum power consumption can get the relationship between r and r, and then use r and resistance formula to calculate l, this is the solution idea. Of course, I can also write to you if you need a detailed answer.

The answer is A, first analyze the scribing to move to the left, the resistance of the sliding rheostat becomes smaller, the resistance of the fixed value resistance R remains unchanged, so the total resistance becomes smaller, according to Ohm's law, so the total current becomes larger, the voltage of the sliding rheostat becomes smaller, and because the series circuit R = R1 + R2, so the voltage of the fixed value resistance R becomes larger, the indicator of meter A becomes larger, and the indicator of meter V becomes larger, so C and D are excluded. The dicing moves to the right Gaosen, the resistance of the sliding rheostat becomes larger, and the resistance value of the fixed value resistance r remains unchanged, so the total resistance becomes larger according to Ohm's law, so the total current becomes smaller, and the voltage of the sliding rheostat becomes larger, and because of the series commotion and defeat circuit r=r1+r2, the fixed value resistance r voltage becomes smaller, the indicator of meter A becomes smaller, and the indicator of meter V becomes smaller, so B is also wrong, only A is correct. Thank you, Qi Zhimu!

S1S2 is closed. R2 is short-circuited.

So r1=u i=9

s2 is disconnected. r1r1 series,.

i=u/r1=6/6=1a

r2=u/i=（9-6）/1=3

Choosing B because when S1 and S2 are closed, R2 is short-circuited, and the voltmeter measures the supply voltage.

That is, the power supply voltage is 9V According to Ohm's law: r=u i, so r1=9v ohm.

When S2 breaks S1 closes.

Series circuits. The sum of the voltages at both ends of each appliance in the series circuit = the power supply voltage, so the voltage at both ends of R2 = 3V

Using the formula i=u r, the current at this time is 1A

Because of the tandem. Therefore, the current passing through the individual appliances is equal.

So according to the formula r=u i-3 ohms.

Let's sort it out: r1 = 6 ohms and r2 = 3 ohms.

So choose B