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Electric Potential and Potential Difference

This category gathers questions that examine the fundamentals of electric potential and potential difference. Topics include how voltage is defined, calculations involving energy per charge, and the relationship between electric fields and potential. Ideal for students reviewing core physics concepts.

30 questions

A spherical conductor of radius 25 cm has a charge of \( 10 \times 10^{-8} \, \text{C} \). What is the electric field at

**Potential due to point charge** V = (1/4π ε₀)Q/r, positive Q gives positive V, negative gives negative. At r=0.3 m from Q=3×10⁻⁸ C, V=9×10⁹×3×10⁻⁸/0.3=900 V. Work done moving charge q from infinity (V=0) to point where V=40 V is W = q V =9×10⁻⁶×40=3.6×10⁻⁴ J. For r = 0.6 m > R = 0.25 m , E = (1/4 π ε₀) (Q/r²) . E = 9 × 10⁹ × (10 × 10⁻⁸/(0.6)²) = 9 × 10⁹ × (10 × 10⁻⁸/0.36) = 2.5 × 10³ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

Two charges \( 8 \, \mu\text{C} \) and \( -4 \, \mu\text{C} \) are at \( (6, 0, 0) \) and \( (-6, 0, 0) \, \text{cm} \).

**Potential due to point charge** V = (1/4π ε₀)Q/r, positive Q gives positive V, negative gives negative. At r=0.3 m from Q=3×10⁻⁸ C, V=9×10⁹×3×10⁻⁸/0.3=900 V. Work done moving charge q from infinity (V=0) to point where V=40 V is W = q V =9×10⁻⁶×40=3.6×10⁻⁴ J. Distance to midpoint = 0.06 m. V = 9 × 10⁹ ( (8 × 10⁻⁶/0.06) + (-4 × 10⁻⁶/0.06) ) = 9 × 10⁹ × (4 × 10⁻⁶/0.06) . V = 9 × 10⁹ × (4 × 10⁻⁶/0.06) = 6 × 10⁵ V . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series,

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A spherical conductor of radius 30 cm has a charge of \( 12 \times 10^{-8} \, \text{C} \). What is the electric field at

**Electric potential** V = k Q/r, k = 1/(4π ε₀)=9×10⁹ N·m²/C², Q charge (C), r distance (m), scalar, potential at surface of spherical conductor radius R, V = k Q/R. Potential difference ΔV = V_B - V_A = -∫ E·dl, work per unit charge to move charge without acceleration. For r = 0.7 m > R = 0.3 m , E = (1/4 π ε₀) (Q/r²) . E = 9 × 10⁹ × (12 × 10⁻⁸/(0.7)²) = 9 × 10⁹ × (12 × 10⁻⁸/0.49) ≈ 2.204 × 10³ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

Three charges \( +5 \, \mu\text{C} \), \( -2 \, \mu\text{C} \), and \( +3 \, \mu\text{C} \) are at \( (0, 0, 0) \), \( (

**Potential due to point charge** V = (1/4π ε₀)Q/r, positive Q gives positive V, negative gives negative. At r=0.3 m from Q=3×10⁻⁸ C, V=9×10⁹×3×10⁻⁸/0.3=900 V. Work done moving charge q from infinity (V=0) to point where V=40 V is W = q V =9×10⁻⁶×40=3.6×10⁻⁴ J. Distances: r₁ = √(5² + 5²) = 5√(2) m , r₂ = 5 m , r₃ = 5 m . V = 9 × 10⁹ ( (5 × 10⁻⁶/5√(2)) + (-2 × 10⁻⁶/5) + (3 × 10⁻⁶/5) ) . V = 9 × 10⁹ ( (5 × 10⁻⁶/7.07) - (2 × 10⁻⁶/5) + (3 × 10⁻⁶/5) ) . V =

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A charge of \( 8 \, \mu\text{C} \) is moved from infinity to a point where the potential is \( 50 \, \text{V} \). What i

**Electric potential** V = k Q/r, k = 1/(4π ε₀)=9×10⁹ N·m²/C², Q charge (C), r distance (m), scalar, potential at surface of spherical conductor radius R, V = k Q/R. Potential difference ΔV = V_B - V_A = -∫ E·dl, work per unit charge to move charge without acceleration. Work done = Potential energy = q V . W = 8 × 10⁻⁶ × 50 = 4 × 10⁻⁴ J = 0.4 mJ . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½ C V² and common potential V = Q_total/C_total,

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A charged conductor is surrounded by a thin concentric hollow conducting shell. If the shell is grounded, what happens t

**Electric potential** V = k Q/r, k = 1/(4π ε₀)=9×10⁹ N·m²/C², Q charge (C), r distance (m), scalar, potential at surface of spherical conductor radius R, V = k Q/R. Potential difference ΔV = V_B - V_A = -∫ E·dl, work per unit charge to move charge without acceleration. When the outer shell is grounded (potential V = 0 ), the potential on the inner conductor adjusts due to charge redistribution. If the inner conductor has charge Q , the inner surface of the shell induces -Q , and since the shell's potential is zero, the outer surface of the shell acquires +Q . The

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A spherical conductor of radius 6 cm has a charge of \( 6 \times 10^{-8} \, \text{C} \). What is the potential at its su

**Spherical conductor** behaves as point charge outside, potential V = k Q/R at surface, field E = k Q/r² for r>R, zero inside for rR, so E = k Q/r² =9×10⁹×6×10⁻⁸/0.16=3375 N/C. Potential at the surface: V = (1/4 π ε₀) (Q/R) . V = 9 × 10⁹ × (6 × 10⁻⁸/0.06) = 9 × 10⁹ × 10⁻⁶ = 9000 V . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½ C V² and common potential V = Q_total/C_total, result

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

Two charges \( 10 \, \mu\text{C} \) and \( -2 \, \mu\text{C} \) are at \( (8, 0, 0) \) and \( (-8, 0, 0) \, \text{cm} \)

**Spherical conductor** behaves as point charge outside, potential V = k Q/R at surface, field E = k Q/r² for r>R, zero inside for rR, so E = k Q/r² =9×10⁹×6×10⁻⁸/0.16=3375 N/C. Distance to midpoint = 0.08 m. V = 9 × 10⁹ ( (10 × 10⁻⁶/0.08) + (-2 × 10⁻⁶/0.08) ) = 9 × 10⁹ × (8 × 10⁻⁶/0.08) . V = 9 × 10⁹ × (8 × 10⁻⁶/0.08) = 9 × 10⁵ V . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq =

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

Three charges \( +8 \, \mu\text{C} \), \( -5 \, \mu\text{C} \), and \( +3 \, \mu\text{C} \) are at \( (0, 0, 0) \), \( (

**Electric potential** V = k Q/r, k = 1/(4π ε₀)=9×10⁹ N·m²/C², Q charge (C), r distance (m), scalar, potential at surface of spherical conductor radius R, V = k Q/R. Potential difference ΔV = V_B - V_A = -∫ E·dl, work per unit charge to move charge without acceleration. Distances: r₁ = √(8² + 8²) = 8√(2) m , r₂ = 8 m , r₃ = 8 m . V = 9 × 10⁹ ( (8 × 10⁻⁶/8√(2)) + (-5 × 10⁻⁶/8) + (3 × 10⁻⁶/8) ) . V = 9 × 10⁹ ( (8 × 10⁻⁶/11.314) - (5 × 10⁻⁶/8) + (3 × 10⁻⁶/8)

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A conductor has a surface charge density of \( 3 \times 10^{-6} \, \text{C/m}^2 \). What is the electric field just outs

**Potential due to point charge** V = (1/4π ε₀)Q/r, positive Q gives positive V, negative gives negative. At r=0.3 m from Q=3×10⁻⁸ C, V=9×10⁹×3×10⁻⁸/0.3=900 V. Work done moving charge q from infinity (V=0) to point where V=40 V is W = q V =9×10⁻⁶×40=3.6×10⁻⁴ J. E = (sigma/ε₀) = (3 × 10⁻⁶/8.85 × 10⁻¹²) ≈ 3.39 × 10⁵ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½ C V² and common potential V = Q_total/C_total, result 3.39 × 10⁵ N/C follows, reflecting potential-capacitance relations.

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A conductor has a surface charge density of \( 5 \times 10^{-7} \, \text{C/m}^2 \). What is the electric field just outs

**Spherical conductor** behaves as point charge outside, potential V = k Q/R at surface, field E = k Q/r² for r>R, zero inside for rR, so E = k Q/r² =9×10⁹×6×10⁻⁸/0.16=3375 N/C. E = (sigma/ε₀) = (5 × 10⁻⁷/8.85 × 10⁻¹²) ≈ 5.65 × 10⁴ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½ C V² and common potential V = Q_total/C_total, result 5.65 × 10⁴ N/C follows, reflecting potential-capacitance relations.

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference

A conductor has a surface charge density of \( 2.5 \times 10^{-6} \, \text{C/m}^2 \). What is the electric field just ou

**Potential due to point charge** V = (1/4π ε₀)Q/r, positive Q gives positive V, negative gives negative. At r=0.3 m from Q=3×10⁻⁸ C, V=9×10⁹×3×10⁻⁸/0.3=900 V. Work done moving charge q from infinity (V=0) to point where V=40 V is W = q V =9×10⁻⁶×40=3.6×10⁻⁴ J. E = (sigma/ε₀) = (2.5 × 10⁻⁶/8.85 × 10⁻¹²) ≈ 2.82 × 10⁵ N/C . Using V = kQ/r, U = k q₁q₂/r, E = -dV/dr, C = ε₀A/d, 1/C_eq series, C_eq = ΣC parallel, U = ½ C V² and common potential V = Q_total/C_total, result 2.82 × 10⁵ N/C follows, reflecting potential-capacitance relations.

Ref: NCERT > Physics Book > Electrostatic Potential and Capacitance > Electric Potential and Potential Difference