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Multiple choice physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

A thermistor:

  1. Is a thermally sensitive resistor

  2. Is made of a semiconductor

  3. Has negative temperature coefficient of resistance

  4. All the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
A thermistor is a type of resistor whose resistance depends on temperature, more than in standard resistor. The word is a combination of thermal and resistor. They are widely used as inrush current limiters, temperature sensors, self -resetting overcurrent protectors, and self-regulating heating elements.
It is made up of semiconductors and has a negative temperature coefficient of resistance.
Multiple choice physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Thermistor material is pressed ________

  1. under zero pressure

  2. under low pressure

  3. under high pressure

  4. under low volume
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A thermistor material is usually pressed under high pressure to form a flat cylindrical shape. Disks and washers are placed in series or in parallel to increase the power dissipation.

Multiple choice physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Thermistors have ________

  1. positive temperature coefficient

  2. negative temperature coefficient

  3. zero temperature coefficien

  4. infinite temperature coefficient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Thermistor generally has a negative temperature coefficient of resistance. With increase in temperature, resistance of a thermistor decreases.

Multiple choice physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Thermistor follows which law for small variations ________

  1. Charles law

  2. KVL

  3. KCL

  4. Ohms law
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For small changes in the values of current, voltage across a thermistor increases. It attains a peak value. Then the voltage across the thermistor decreases. As a result Ohms law is followed at small variations of current.

Multiple choice physics magnetic effect of electric current oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following is/are correct?

  1. Electric current can produce a magnetism

  2. Due to change in current the magnetic strength changes

  3. Magnetic strength of a magnet is independent of the number of turn in the current carrying coil

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

I)According to Oersted experiment electric current can produce magnetism.

iI)Magnetic induction $B \alpha I$
If current changes the strength $B$ changes.
iiI)For circular coil magnetic field $B$ due to single ring $B=\dfrac{\mu _0 i}{2r}$
If magnet contain n turn then its strength is $B _2=nB$
But if current carrying coil have $n _2$ turn then strength doesn't change.
$B _2=nB$
Hence all options are correct.

Multiple choice physics magnetic effect of electric current oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

A compass needle placed at a distance $r$ from a short magnet in $\tan\ A$ position shown a deflection of $60^{o}$. If the distance is increased to $r(3)^{1/3}$, then the deflected of the compass needle is:

  1. $30^{o}$
  2. $60^{o}\ \times (3)^{1/3}$
  3. $60^{o}\ \times (3)^{2/3}$
  4. $90^{o}\ \times (3)^{1/3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a short magnet in the tan A position, the magnetic field B is proportional to 1/r^3. Since B = B_h * tan(theta), tan(theta) is proportional to 1/r^3. If r increases to r * (3)^(1/3), r^3 increases by a factor of 3, so tan(theta) decreases by a factor of 3. tan(60) = sqrt(3), so the new tan(theta) = sqrt(3)/3 = 1/sqrt(3), which corresponds to 30 degrees.

Multiple choice physics magnetic effect of electric current oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Electromagnet can be formed due to which of the following?

  1. Heating effect of current

  2. Magnetic effect of current

  3. Chemical effect of current

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electromagnets are formed by passing an electric current through a wire coiled around the substance with iron core. The electric current generates a magnetic field around the  substance and thus magnetize it which convert it into a magnet. Thus electromagnet can be formed due to the magnetic effect of current.